diff --git a/icu4c/source/common/unicode/utypes.h b/icu4c/source/common/unicode/utypes.h
index 87fa5ddf7e87..0151ebd47015 100644
--- a/icu4c/source/common/unicode/utypes.h
+++ b/icu4c/source/common/unicode/utypes.h
@@ -597,15 +597,13 @@ typedef enum UErrorCode {
     U_MF_MISSING_SELECTOR_ANNOTATION_ERROR,  /**< A selector expression evaluates to an unannotated operand. @internal ICU 75 technology preview @deprecated This API is for technology preview only. */
     U_MF_DUPLICATE_DECLARATION_ERROR, /**< The same variable is declared in more than one .local or .input declaration. @internal ICU 75 technology preview @deprecated This API is for technology preview only. */
     U_MF_OPERAND_MISMATCH_ERROR,     /**< An operand provided to a function does not have the required form for that function @internal ICU 75 technology preview @deprecated This API is for technology preview only. */
-    U_MF_UNSUPPORTED_STATEMENT_ERROR, /**< A message includes a reserved statement. @internal ICU 75 technology preview @deprecated This API is for technology preview only. */
-    U_MF_UNSUPPORTED_EXPRESSION_ERROR, /**< A message includes syntax reserved for future standardization or private implementation use. @internal ICU 75 technology preview @deprecated This API is for technology preview only. */
     U_MF_DUPLICATE_VARIANT_ERROR, /**< A message includes a variant with the same key list as another variant. @internal ICU 76 technology preview @deprecated This API is for technology preview only. */
 #ifndef U_HIDE_DEPRECATED_API
     /**
      * One more than the highest normal formatting API error code.
      * @deprecated ICU 58 The numeric value may change over time, see ICU ticket #12420.
      */
-    U_FMT_PARSE_ERROR_LIMIT = 0x10122,
+    U_FMT_PARSE_ERROR_LIMIT = 0x10120,
 #endif  // U_HIDE_DEPRECATED_API
 
     /*
diff --git a/icu4c/source/common/utypes.cpp b/icu4c/source/common/utypes.cpp
index 2f449ffea033..4602314147f1 100644
--- a/icu4c/source/common/utypes.cpp
+++ b/icu4c/source/common/utypes.cpp
@@ -140,8 +140,6 @@ _uFmtErrorName[U_FMT_PARSE_ERROR_LIMIT - U_FMT_PARSE_ERROR_START] = {
     "U_MF_MISSING_SELECTOR_ANNOTATION_ERROR",
     "U_MF_DUPLICATE_DECLARATION_ERROR",
     "U_MF_OPERAND_MISMATCH_ERROR",
-    "U_MF_UNSUPPORTED_STATEMENT_ERROR",
-    "U_MF_UNSUPPORTED_EXPRESSION_ERROR",
     "U_MF_DUPLICATE_VARIANT_ERROR"
 };
 
diff --git a/icu4c/source/i18n/messageformat2.cpp b/icu4c/source/i18n/messageformat2.cpp
index 2febdf0ade15..73f7fa45e69f 100644
--- a/icu4c/source/i18n/messageformat2.cpp
+++ b/icu4c/source/i18n/messageformat2.cpp
@@ -241,24 +241,6 @@ FunctionOptions MessageFormatter::resolveOptions(const Environment& env, const O
     return FormattedPlaceholder(fallback);
 }
 
-// Per https://github.com/unicode-org/message-format-wg/blob/main/spec/formatting.md#fallback-resolution
-static UnicodeString reservedFallback (const Expression& e) {
-    UErrorCode localErrorCode = U_ZERO_ERROR;
-    const Operator* rator = e.getOperator(localErrorCode);
-    U_ASSERT(U_SUCCESS(localErrorCode));
-    const Reserved& r = rator->asReserved();
-
-    // An empty Reserved isn't representable in the syntax
-    U_ASSERT(r.numParts() > 0);
-
-    const UnicodeString& contents = r.getPart(0).unquoted();
-    // Parts should never be empty
-    U_ASSERT(contents.length() > 0);
-
-    // Return first character of string
-    return UnicodeString(contents, 0, 1);
-}
-
 // Formats an expression using `globalEnv` for the values of variables
 [[nodiscard]] FormattedPlaceholder MessageFormatter::formatExpression(const Environment& globalEnv,
                                                                 const Expression& expr,
@@ -268,12 +250,6 @@ static UnicodeString reservedFallback (const Expression& e) {
         return {};
     }
 
-    // Formatting error
-    if (expr.isReserved()) {
-        context.getErrors().setReservedError(status);
-        return FormattedPlaceholder(reservedFallback(expr));
-    }
-
     const Operand& rand = expr.getOperand();
     // Format the operand (formatOperand handles the case of a null operand)
     FormattedPlaceholder randVal = formatOperand(globalEnv, rand, context, status);
@@ -675,12 +651,6 @@ ResolvedSelector MessageFormatter::resolveVariables(const Environment& env,
         return {};
     }
 
-    // A `reserved` is an error
-    if (expr.isReserved()) {
-        context.getErrors().setReservedError(status);
-        return ResolvedSelector(FormattedPlaceholder(reservedFallback(expr)));
-    }
-
     // Function call -- resolve the operand and options
     if (expr.isFunctionCall()) {
         const Operator* rator = expr.getOperator(status);
diff --git a/icu4c/source/i18n/messageformat2_checker.cpp b/icu4c/source/i18n/messageformat2_checker.cpp
index 824b798410d5..bdc5c383b6e8 100644
--- a/icu4c/source/i18n/messageformat2_checker.cpp
+++ b/icu4c/source/i18n/messageformat2_checker.cpp
@@ -136,9 +136,7 @@ void Checker::addFreeVars(TypeEnvironment& t, const OptionMap& opts, UErrorCode&
 void Checker::addFreeVars(TypeEnvironment& t, const Operator& rator, UErrorCode& status) {
     CHECK_ERROR(status);
 
-    if (!rator.isReserved()) {
-        addFreeVars(t, rator.getOptionsInternal(), status);
-    }
+    addFreeVars(t, rator.getOptionsInternal(), status);
 }
 
 void Checker::addFreeVars(TypeEnvironment& t, const Expression& rhs, UErrorCode& status) {
@@ -213,12 +211,10 @@ void Checker::requireAnnotated(const TypeEnvironment& t, const Expression& selec
     if (selectorExpr.isFunctionCall()) {
         return; // No error
     }
-    if (!selectorExpr.isReserved()) {
-        const Operand& rand = selectorExpr.getOperand();
-        if (rand.isVariable()) {
-            if (t.get(rand.asVariable()) == TypeEnvironment::Type::Annotated) {
-                return; // No error
-            }
+    const Operand& rand = selectorExpr.getOperand();
+    if (rand.isVariable()) {
+        if (t.get(rand.asVariable()) == TypeEnvironment::Type::Annotated) {
+            return; // No error
         }
     }
     // If this code is reached, an error was detected
@@ -240,9 +236,6 @@ TypeEnvironment::Type typeOf(TypeEnvironment& t, const Expression& expr) {
     if (expr.isFunctionCall()) {
         return TypeEnvironment::Type::Annotated;
     }
-    if (expr.isReserved()) {
-        return TypeEnvironment::Type::Unannotated;
-    }
     const Operand& rand = expr.getOperand();
     U_ASSERT(!rand.isNull());
     if (rand.isLiteral()) {
@@ -296,11 +289,6 @@ void Checker::checkDeclarations(TypeEnvironment& t, UErrorCode& status) {
         // Next, extend the type environment with a binding from lhs to its type
         t.extend(lhs, typeOf(t, rhs), status);
     }
-
-    // Check for unsupported statements
-    if (dataModel.unsupportedStatementsLen > 0) {
-        errors.addError(StaticErrorType::UnsupportedStatementError, status);
-    }
 }
 
 void Checker::check(UErrorCode& status) {
diff --git a/icu4c/source/i18n/messageformat2_data_model.cpp b/icu4c/source/i18n/messageformat2_data_model.cpp
index 523ff1b39384..3fe5f65b5323 100644
--- a/icu4c/source/i18n/messageformat2_data_model.cpp
+++ b/icu4c/source/i18n/messageformat2_data_model.cpp
@@ -199,77 +199,6 @@ const Literal& Key::asLiteral() const {
 
 Key::~Key() {}
 
-// ------------ Reserved
-
-// Copy constructor
-Reserved::Reserved(const Reserved& other) : len(other.len) {
-    U_ASSERT(!other.bogus);
-
-    UErrorCode localErrorCode = U_ZERO_ERROR;
-    if (len == 0) {
-        parts.adoptInstead(nullptr);
-    } else {
-        parts.adoptInstead(copyArray(other.parts.getAlias(), len, localErrorCode));
-    }
-    if (U_FAILURE(localErrorCode)) {
-        bogus = true;
-    }
-}
-
-Reserved& Reserved::operator=(Reserved other) noexcept {
-    swap(*this, other);
-    return *this;
-}
-
-Reserved::Reserved(const UVector& ps, UErrorCode& status) noexcept : len(ps.size()) {
-    if (U_FAILURE(status)) {
-        return;
-    }
-    parts = LocalArray<Literal>(copyVectorToArray<Literal>(ps, status));
-}
-
-int32_t Reserved::numParts() const {
-    U_ASSERT(!bogus);
-    return len;
-}
-
-const Literal& Reserved::getPart(int32_t i) const {
-    U_ASSERT(!bogus);
-    U_ASSERT(i < numParts());
-    return parts[i];
-}
-
-Reserved::Builder::Builder(UErrorCode& status) {
-    parts = createUVector(status);
-}
-
-Reserved Reserved::Builder::build(UErrorCode& status) const noexcept {
-    if (U_FAILURE(status)) {
-        return {};
-    }
-    U_ASSERT(parts != nullptr);
-    return Reserved(*parts, status);
-}
-
-Reserved::Builder& Reserved::Builder::add(Literal&& part, UErrorCode& status) noexcept {
-    U_ASSERT(parts != nullptr);
-    if (U_SUCCESS(status)) {
-        Literal* l = create<Literal>(std::move(part), status);
-        parts->adoptElement(l, status);
-    }
-    return *this;
-}
-
-Reserved::Builder::~Builder() {
-    if (parts != nullptr) {
-        delete parts;
-    }
-}
-
-Reserved::~Reserved() {
-    len = 0;
-}
-
 //------------------------ Operator
 
 OptionMap::OptionMap(const UVector& opts, UErrorCode& status) : len(opts.size()) {
@@ -379,14 +308,8 @@ OptionMap::Builder::~Builder() {
     }
 }
 
-const Reserved& Operator::asReserved() const {
-    U_ASSERT(isReserved());
-    return *(std::get_if<Reserved>(&contents));
-}
-
 const OptionMap& Operator::getOptionsInternal() const {
-    U_ASSERT(!isReserved());
-    return std::get_if<Callable>(&contents)->getOptions();
+    return options;
 }
 
 Option::Option(const Option& other): name(other.name), rand(other.rand) {}
@@ -400,62 +323,28 @@ Option::~Option() {}
 
 Operator::Builder::Builder(UErrorCode& status) : options(OptionMap::Builder(status)) {}
 
-Operator::Builder& Operator::Builder::setReserved(Reserved&& reserved) {
-    isReservedSequence = true;
-    hasFunctionName = false;
-    hasOptions = false;
-    asReserved = std::move(reserved);
-    return *this;
-}
-
 Operator::Builder& Operator::Builder::setFunctionName(FunctionName&& func) {
-    isReservedSequence = false;
-    hasFunctionName = true;
     functionName = std::move(func);
     return *this;
 }
 
 const FunctionName& Operator::getFunctionName() const {
-    U_ASSERT(!isReserved());
-    return std::get_if<Callable>(&contents)->getName();
+    return name;
 }
 
 Operator::Builder& Operator::Builder::addOption(const UnicodeString &key, Operand&& value, UErrorCode& errorCode) noexcept {
     THIS_ON_ERROR(errorCode);
 
-    isReservedSequence = false;
-    hasOptions = true;
     options.add(Option(key, std::move(value)), errorCode);
     return *this;
 }
 
 Operator Operator::Builder::build(UErrorCode& errorCode) {
-    Operator result;
-    if (U_FAILURE(errorCode)) {
-        return result;
-    }
-    // Must be either reserved or function, not both; enforced by methods
-    if (isReservedSequence) {
-        // Methods enforce that the function name and options are unset
-        // if `setReserved()` is called, so if they were valid, that
-        // would indicate a bug.
-        U_ASSERT(!hasOptions && !hasFunctionName);
-        result = Operator(asReserved);
-    } else {
-        if (!hasFunctionName) {
-            // Neither function name nor reserved was set
-            // There is no default, so this case could occur if the
-            // caller creates a builder and doesn't make any calls
-            // before calling build().
-            errorCode = U_INVALID_STATE_ERROR;
-            return result;
-        }
-        result = Operator(functionName, options.build(errorCode));
-    }
-    return result;
+    return Operator(functionName, options.build(errorCode));
 }
 
-Operator::Operator(const Operator& other) noexcept : contents(other.contents) {}
+Operator::Operator(const Operator& other) noexcept
+    : name(other.name), options(other.options) {}
 
 Operator& Operator::operator=(Operator other) noexcept {
     swap(*this, other);
@@ -463,23 +352,13 @@ Operator& Operator::operator=(Operator other) noexcept {
 }
 
 // Function call
-Operator::Operator(const FunctionName& f, const UVector& optsVector, UErrorCode& status) : contents(Callable(f, OptionMap(optsVector, status))) {}
 
-Operator::Operator(const FunctionName& f, const OptionMap& opts) : contents(Callable(f, opts)) {}
+Operator::Operator(const FunctionName& f, const OptionMap& opts) : name(f), options(opts) {}
 
 Operator::Builder::~Builder() {}
 
 Operator::~Operator() {}
 
-Callable& Callable::operator=(Callable other) noexcept {
-    swap(*this, other);
-    return *this;
-}
-
-Callable::Callable(const Callable& other) : name(other.name), options(other.options) {}
-
-Callable::~Callable() {}
-
 // ------------ Markup
 
 Markup::Builder::Builder(UErrorCode& status)
@@ -538,19 +417,14 @@ UBool Expression::isStandaloneAnnotation() const {
 
 // Returns true for function calls with operands as well as
 // standalone annotations.
-// Reserved sequences are not function calls
 UBool Expression::isFunctionCall() const {
-    return (rator.has_value() && !rator->isReserved());
-}
-
-UBool Expression::isReserved() const {
-    return (rator.has_value() && rator->isReserved());
+    return rator.has_value();
 }
 
 const Operator* Expression::getOperator(UErrorCode& status) const {
     NULL_ON_ERROR(status);
 
-    if (!(isReserved() || isFunctionCall())) {
+    if (!isFunctionCall()) {
         status = U_INVALID_STATE_ERROR;
         return nullptr;
     }
@@ -617,92 +491,6 @@ Expression::Builder::~Builder() {}
 
 Expression::~Expression() {}
 
-// ----------- UnsupportedStatement
-
-UnsupportedStatement::Builder::Builder(UErrorCode& status) {
-    expressions = createUVector(status);
-}
-
-UnsupportedStatement::Builder& UnsupportedStatement::Builder::setKeyword(const UnicodeString& k) {
-    keyword = k;
-    return *this;
-}
-
-UnsupportedStatement::Builder& UnsupportedStatement::Builder::setBody(Reserved&& r) {
-    body.emplace(r);
-    return *this;
-}
-
-UnsupportedStatement::Builder& UnsupportedStatement::Builder::addExpression(Expression&& e, UErrorCode& status) {
-    U_ASSERT(expressions != nullptr);
-    if (U_SUCCESS(status)) {
-        Expression* expr = create<Expression>(std::move(e), status);
-        expressions->adoptElement(expr, status);
-    }
-    return *this;
-}
-
-UnsupportedStatement UnsupportedStatement::Builder::build(UErrorCode& status) const {
-    if (U_SUCCESS(status)) {
-        U_ASSERT(expressions != nullptr);
-        if (keyword.length() <= 0) {
-            status = U_ILLEGAL_ARGUMENT_ERROR;
-        } else if (expressions->size() < 1) {
-            status = U_ILLEGAL_ARGUMENT_ERROR;
-        } else {
-            return UnsupportedStatement(keyword, body, *expressions, status);
-        }
-    }
-    return {};
-}
-
-const Reserved* UnsupportedStatement::getBody(UErrorCode& errorCode) const {
-    if (U_SUCCESS(errorCode)) {
-        if (body.has_value()) {
-            return &(*body);
-        }
-        errorCode = U_ILLEGAL_ARGUMENT_ERROR;
-    }
-    return nullptr;
-}
-
-UnsupportedStatement::UnsupportedStatement(const UnicodeString& k,
-                                           const std::optional<Reserved>& r,
-                                           const UVector& es,
-                                           UErrorCode& status)
-    : keyword(k), body(r), expressionsLen(es.size()) {
-    CHECK_ERROR(status);
-
-    U_ASSERT(expressionsLen >= 1);
-    Expression* result = copyVectorToArray<Expression>(es, status);
-    CHECK_ERROR(status);
-    expressions.adoptInstead(result);
-}
-
-UnsupportedStatement::UnsupportedStatement(const UnsupportedStatement& other) {
-    keyword = other.keyword;
-    body = other.body;
-    expressionsLen = other.expressionsLen;
-    U_ASSERT(expressionsLen > 0);
-    UErrorCode localErrorCode = U_ZERO_ERROR;
-    expressions.adoptInstead(copyArray(other.expressions.getAlias(), expressionsLen, localErrorCode));
-    if (U_FAILURE(localErrorCode)) {
-        expressionsLen = 0;
-    }
-}
-
-UnsupportedStatement& UnsupportedStatement::operator=(UnsupportedStatement other) noexcept {
-    swap(*this, other);
-    return *this;
-}
-
-UnsupportedStatement::Builder::~Builder() {
-    if (expressions != nullptr) {
-        delete expressions;
-    }
-}
-
-UnsupportedStatement::~UnsupportedStatement() {}
 // ----------- PatternPart
 
 // PatternPart needs a copy constructor in order to make Pattern deeply copyable
@@ -844,7 +632,7 @@ const Expression& Binding::getValue() const {
             if (hasOperator) {
                 rator = b.getValue().getOperator(errorCode);
                 U_ASSERT(U_SUCCESS(errorCode));
-                b.annotation = &rator->contents;
+                b.annotation = rator;
             } else {
                 b.annotation = nullptr;
             }
@@ -856,18 +644,17 @@ const Expression& Binding::getValue() const {
 
 const OptionMap& Binding::getOptionsInternal() const {
     U_ASSERT(annotation != nullptr);
-    U_ASSERT(std::holds_alternative<Callable>(*annotation));
-    return std::get_if<Callable>(annotation)->getOptions();
+    return annotation->getOptionsInternal();
 }
 
 void Binding::updateAnnotation() {
     UErrorCode localErrorCode = U_ZERO_ERROR;
     const Operator* rator = expr.getOperator(localErrorCode);
-    if (U_FAILURE(localErrorCode) || rator->isReserved()) {
+    if (U_FAILURE(localErrorCode)) {
         return;
     }
-    U_ASSERT(U_SUCCESS(localErrorCode) && !rator->isReserved());
-    annotation = &rator->contents;
+    U_ASSERT(U_SUCCESS(localErrorCode));
+    annotation = rator;
 }
 
 Binding::Binding(const Binding& other) : var(other.var), expr(other.expr), local(other.local) {
@@ -949,17 +736,8 @@ const Variant* MFDataModel::getVariantsInternal() const {
     return std::get_if<Matcher>(&body)->variants.getAlias();
 }
 
-// Returns nullptr if no unsupported statements
-const UnsupportedStatement* MFDataModel::getUnsupportedStatementsInternal() const {
-    U_ASSERT(!bogus);
-    U_ASSERT(unsupportedStatementsLen == 0 || unsupportedStatements != nullptr);
-    return unsupportedStatements.getAlias();
-}
-
-
 MFDataModel::Builder::Builder(UErrorCode& status) {
     bindings = createUVector(status);
-    unsupportedStatements = createUVector(status);
 }
 
 // Invalidate pattern and create selectors/variants if necessary
@@ -1008,14 +786,6 @@ MFDataModel::Builder& MFDataModel::Builder::addBinding(Binding&& b, UErrorCode&
     return *this;
 }
 
-MFDataModel::Builder& MFDataModel::Builder::addUnsupportedStatement(UnsupportedStatement&& s, UErrorCode& status) {
-    if (U_SUCCESS(status)) {
-        U_ASSERT(unsupportedStatements != nullptr);
-        unsupportedStatements->adoptElement(create<UnsupportedStatement>(std::move(s), status), status);
-    }
-    return *this;
-}
-
 /*
   selector must be non-null
 */
@@ -1077,10 +847,6 @@ MFDataModel::MFDataModel(const MFDataModel& other) : body(Pattern()) {
     if (bindingsLen > 0) {
         bindings.adoptInstead(copyArray(other.bindings.getAlias(), bindingsLen, localErrorCode));
     }
-    unsupportedStatementsLen = other.unsupportedStatementsLen;
-    if (unsupportedStatementsLen > 0) {
-        unsupportedStatements.adoptInstead(copyArray(other.unsupportedStatements.getAlias(), unsupportedStatementsLen, localErrorCode));
-    }
     if (U_FAILURE(localErrorCode)) {
         bogus = true;
     }
@@ -1110,11 +876,6 @@ MFDataModel::MFDataModel(const MFDataModel::Builder& builder, UErrorCode& errorC
     if (bindingsLen > 0) {
         bindings.adoptInstead(copyVectorToArray<Binding>(*builder.bindings, errorCode));
     }
-    unsupportedStatementsLen = builder.unsupportedStatements->size();
-    if (unsupportedStatementsLen > 0) {
-        unsupportedStatements.adoptInstead(copyVectorToArray<UnsupportedStatement>(*builder.unsupportedStatements,
-                                                                                   errorCode));
-    }
     if (U_FAILURE(errorCode)) {
         bogus = true;
     }
@@ -1149,9 +910,6 @@ MFDataModel::Builder::~Builder() {
     if (bindings != nullptr) {
         delete bindings;
     }
-    if (unsupportedStatements != nullptr) {
-        delete unsupportedStatements;
-    }
 }
 } // namespace message2
 
diff --git a/icu4c/source/i18n/messageformat2_errors.cpp b/icu4c/source/i18n/messageformat2_errors.cpp
index 32990a670b11..9d1d6bab81a1 100644
--- a/icu4c/source/i18n/messageformat2_errors.cpp
+++ b/icu4c/source/i18n/messageformat2_errors.cpp
@@ -19,10 +19,6 @@ namespace message2 {
     // Errors
     // -----------
 
-    void DynamicErrors::setReservedError(UErrorCode& status) {
-        addError(DynamicError(DynamicErrorType::ReservedError), status);
-    }
-
     void DynamicErrors::setFormattingError(const FunctionName& formatterName, UErrorCode& status) {
         addError(DynamicError(DynamicErrorType::FormattingError, formatterName), status);
     }
@@ -143,10 +139,6 @@ namespace message2 {
                 status = U_MF_OPERAND_MISMATCH_ERROR;
                 break;
             }
-            case DynamicErrorType::ReservedError: {
-                status = U_MF_UNSUPPORTED_EXPRESSION_ERROR;
-                break;
-            }
             case DynamicErrorType::SelectorError: {
                 status = U_MF_SELECTOR_ERROR;
                 break;
@@ -196,10 +188,6 @@ namespace message2 {
             dataModelError = true;
             break;
         }
-        case StaticErrorType::UnsupportedStatementError: {
-            dataModelError = true;
-            break;
-        }
         }
         syntaxAndDataModelErrors->adoptElement(errorP, status);
     }
@@ -228,10 +216,6 @@ namespace message2 {
             resolutionAndFormattingErrors->adoptElement(errorP, status);
             break;
         }
-        case DynamicErrorType::ReservedError: {
-            resolutionAndFormattingErrors->adoptElement(errorP, status);
-            break;
-        }
         case DynamicErrorType::SelectorError: {
             selectorError = true;
             resolutionAndFormattingErrors->adoptElement(errorP, status);
@@ -279,9 +263,6 @@ namespace message2 {
                 status = U_MF_SYNTAX_ERROR;
                 break;
             }
-            case StaticErrorType::UnsupportedStatementError: {
-                status = U_MF_UNSUPPORTED_STATEMENT_ERROR;
-            }
             }
         }
     }
diff --git a/icu4c/source/i18n/messageformat2_errors.h b/icu4c/source/i18n/messageformat2_errors.h
index d1766af184d1..f84aa7362837 100644
--- a/icu4c/source/i18n/messageformat2_errors.h
+++ b/icu4c/source/i18n/messageformat2_errors.h
@@ -58,7 +58,6 @@ namespace message2 {
         MissingSelectorAnnotation,
         NonexhaustivePattern,
         SyntaxError,
-        UnsupportedStatementError,
         VariantKeyMismatchError
     };
 
@@ -66,7 +65,6 @@ namespace message2 {
         UnresolvedVariable,
         FormattingError,
         OperandMismatchError,
-        ReservedError,
         SelectorError,
         UnknownFunction,
     };
@@ -123,7 +121,6 @@ namespace message2 {
 
         int32_t count() const;
         void setSelectorError(const FunctionName&, UErrorCode&);
-        void setReservedError(UErrorCode&);
         void setUnresolvedVariable(const VariableName&, UErrorCode&);
         void setUnknownFunction(const FunctionName&, UErrorCode&);
         void setFormattingError(const FunctionName&, UErrorCode&);
diff --git a/icu4c/source/i18n/messageformat2_parser.cpp b/icu4c/source/i18n/messageformat2_parser.cpp
index ad11324a964d..b4768756c5ea 100644
--- a/icu4c/source/i18n/messageformat2_parser.cpp
+++ b/icu4c/source/i18n/messageformat2_parser.cpp
@@ -104,8 +104,6 @@ static bool inRange(UChar32 c, UChar32 first, UChar32 last) {
 
   `isContentChar()`   : `content-char`
   `isTextChar()`      : `text-char`
-  `isReservedStart()` : `reserved-start`
-  `isReservedChar()`  : `reserved-char`
   `isAlpha()`         : `ALPHA`
   `isDigit()`         : `DIGIT`
   `isNameStart()`     : `name-start`
@@ -149,35 +147,6 @@ static bool isTextChar(UChar32 c) {
         || c == PIPE;
 }
 
-// Note: this doesn't distinguish between private-use
-// and reserved, since the data model doesn't
-static bool isReservedStart(UChar32 c) {
-    switch (c) {
-    case BANG:
-    case PERCENT:
-    case ASTERISK:
-    case PLUS:
-    case LESS_THAN:
-    case GREATER_THAN:
-    case QUESTION:
-    case TILDE:
-    // Private-use
-    case CARET:
-    case AMPERSAND:
-        return true;
-    default:
-        return false;
-    }
-}
-
-static bool isReservedChar(UChar32 c) {
-    return isContentChar(c) || c == PERIOD;
-}
-
-static bool isReservedBodyStart(UChar32 c) {
-    return isReservedChar(c) || c == BACKSLASH || c == PIPE;
-}
-
 static bool isAlpha(UChar32 c) { return inRange(c, 0x0041, 0x005A) || inRange(c, 0x0061, 0x007A); }
 
 static bool isDigit(UChar32 c) { return inRange(c, 0x0030, 0x0039); }
@@ -230,24 +199,7 @@ static bool isFunctionStart(UChar32 c) {
 
 // Returns true iff `c` can begin an `annotation` nonterminal
 static bool isAnnotationStart(UChar32 c) {
-    return isFunctionStart(c) || isReservedStart(c);
-}
-
-// Returns true iff `c` can begin either a `reserved-char` or `reserved-escape`
-// literal
-static bool reservedChunkFollows(UChar32 c) {
-   switch(c) {
-       // reserved-escape
-       case BACKSLASH:
-       // literal
-       case PIPE: {
-           return true;
-       }
-       default: {
-           // reserved-char
-           return (isReservedChar(c));
-       }
-    }
+    return isFunctionStart(c);
 }
 
 // Returns true iff `c` can begin a `literal` nonterminal
@@ -1121,189 +1073,7 @@ Arbitrary lookahead is required to parse attribute lists, similarly to option li
 }
 
 /*
-  Consumes a non-empty sequence of reserved-chars, reserved-escapes, and
-  literals (as in 1*(reserved-char / reserved-escape / literal) in the `reserved-body` rule)
-
-  Appends it to `str`
-*/
-void Parser::parseReservedChunk(Reserved::Builder& result, UErrorCode& status) {
-    CHECK_ERROR(status);
-
-    bool empty = true;
-    UnicodeString chunk;
-    while(reservedChunkFollows(peek())) {
-        empty = false;
-        // reserved-char
-        if (isReservedChar(peek())) {
-            chunk += peek();
-            normalizedInput += peek();
-            // consume the char
-            next();
-            // Restore precondition
-            CHECK_BOUNDS(status);
-            continue;
-        }
-
-        if (chunk.length() > 0) {
-          result.add(Literal(false, chunk), status);
-          chunk.setTo(u"", 0);
-        }
-
-        if (peek() == BACKSLASH) {
-            // reserved-escape
-            result.add(Literal(false, parseEscapeSequence(status)), status);
-            chunk.setTo(u"", 0);
-        } else if (peek() == PIPE || isUnquotedStart(peek())) {
-            result.add(parseLiteral(status), status);
-        } else {
-            // The reserved chunk ends here
-            break;
-        }
-
-        CHECK_ERROR(status); // Avoid looping infinitely
-    }
-
-    // Add the last chunk if necessary
-    if (chunk.length() > 0) {
-        result.add(Literal(false, chunk), status);
-    }
-
-    if (empty) {
-        ERROR(status);
-    }
-}
-
-/*
-  Consume a `reserved-start` character followed by a possibly-empty sequence
-  of non-empty sequences of reserved characters, separated by whitespace.
-  Matches the `reserved` nonterminal in the grammar
-
-*/
-Reserved Parser::parseReserved(UErrorCode& status) {
-    Reserved::Builder builder(status);
-
-    if (U_FAILURE(status)) {
-        return {};
-    }
-
-    U_ASSERT(inBounds());
-
-    // Require a `reservedStart` character
-    if (!isReservedStart(peek())) {
-        ERROR(status);
-        return Reserved();
-    }
-
-    // Add the start char as a separate text chunk
-    UnicodeString firstCharString(peek());
-    builder.add(Literal(false, firstCharString), status);
-    if (U_FAILURE(status)) {
-        return {};
-    }
-    // Consume reservedStart
-    normalizedInput += peek();
-    next();
-    return parseReservedBody(builder, status);
-}
-
-Reserved Parser::parseReservedBody(Reserved::Builder& builder, UErrorCode& status) {
-    if (U_FAILURE(status)) {
-        return {};
-    }
-
-/*
-  Arbitrary lookahead is required to parse a `reserved`, for similar reasons
-  to why it's required for parsing function annotations.
-
-  In the grammar:
-
-  annotation = (function *(s option)) / reserved
-  expression = "{" [s] (((literal / variable) [s annotation]) / annotation) [s] "}"
-  reserved       = reserved-start reserved-body
-  reserved-body  = *( [s] 1*(reserved-char / reserved-escape / literal))
-
-  When reading a whitespace character, it's ambiguous whether it's the optional
-  whitespace in this rule, or the optional whitespace that precedes a '}' in an
-  expression.
-
-  The ambiguity is resolved using the same grammar refactoring as shown in
-  the comment in `parseOptions()`.
-*/
-    // Consume reserved characters / literals / reserved escapes
-    // until a character that can't be in a `reserved-body` is seen
-    while (true) {
-        /*
-          First, if there is whitespace, it means either a chunk follows it,
-          or this is the trailing whitespace before the '}' that terminates an
-          expression.
-
-          Next, if the next character can start a reserved-char, reserved-escape,
-          or literal, then parse a "chunk" of reserved things.
-          In any other case, we exit successfully, since per the refactored
-          grammar rule:
-               annotation = (function *(s option) [s]) / (reserved [s])
-          it's valid to consume whitespace after a `reserved`.
-          (`parseExpression()` is responsible for checking that the next
-          character is in fact a '}'.)
-         */
-        if (!inBounds()) {
-            break;
-        }
-        int32_t numWhitespaceChars = 0;
-        int32_t savedIndex = index;
-        if (isWhitespace(peek())) {
-            parseOptionalWhitespace(status);
-            numWhitespaceChars = index - savedIndex;
-            // Restore precondition
-            if (!inBounds()) {
-                break;
-            }
-        }
-
-        if (reservedChunkFollows(peek())) {
-            parseReservedChunk(builder, status);
-
-            // Avoid looping infinitely
-            if (U_FAILURE(status) || !inBounds()) {
-                break;
-            }
-        } else {
-            if (numWhitespaceChars > 0) {
-                if (peek() == LEFT_CURLY_BRACE) {
-                    // Resolve even more ambiguity (space preceding another piece of
-                    // a `reserved-body`, vs. space preceding an expression in `reserved-statement`
-                    // "Backtrack"
-                    index -= numWhitespaceChars;
-                    break;
-                }
-                if (peek() == RIGHT_CURLY_BRACE) {
-                    // Not an error: just means there's no trailing whitespace
-                    // after this `reserved`
-                    break;
-                }
-                if (peek() == AT) {
-                    // Not an error, but we have to "backtrack" due to the ambiguity
-                    // between an `s` preceding another reserved chunk
-                    // and an `s` preceding an attribute list
-                    index -= numWhitespaceChars;
-                    break;
-                }
-                // Error: if there's whitespace, it must either be followed
-                // by a non-empty sequence or by '}'
-                ERROR(status);
-                break;
-            }
-            // If there was no whitespace, it's not an error,
-            // just the end of the reserved string
-            break;
-        }
-    }
-
-    return builder.build(status);
-}
-
-/*
-  Consume a function call or reserved string, matching the `annotation`
+  Consume a function call, matching the `annotation`
   nonterminal in the grammar
 
   Returns an `Operator` representing this (a reserved is a parse error)
@@ -1323,17 +1093,9 @@ Operator Parser::parseAnnotation(UErrorCode& status) {
         // Consume the options (which may be empty)
         parseOptions(addOptions, status);
     } else {
-      // Must be reserved
-      // A reserved sequence is not a parse error, but might be a formatting error
-      Reserved rator = parseReserved(status);
-      ratorBuilder.setReserved(std::move(rator));
+        ERROR(status);
     }
-    UErrorCode localStatus = U_ZERO_ERROR;
-    Operator result = ratorBuilder.build(localStatus);
-    // Either `setReserved` or `setFunctionName` was called,
-    // so there shouldn't be an error.
-    U_ASSERT(U_SUCCESS(localStatus));
-    return result;
+    return ratorBuilder.build(status);
 }
 
 /*
@@ -1613,95 +1375,6 @@ void Parser::parseInputDeclaration(UErrorCode& status) {
     }
 }
 
-/*
-  Parses a `reserved-statement` per the grammar
- */
-void Parser::parseUnsupportedStatement(UErrorCode& status) {
-    U_ASSERT(inBounds() && peek() == PERIOD);
-
-    UnsupportedStatement::Builder builder(status);
-    CHECK_ERROR(status);
-
-    // Parse the keyword
-    UnicodeString keyword(PERIOD);
-    normalizedInput += UnicodeString(PERIOD);
-    next();
-    keyword += parseName(status);
-    builder.setKeyword(keyword);
-
-    // Parse the body, which is optional
-    // Lookahead is required to distinguish the `s` in reserved-body
-    // from the `s` in `[s] expression`
-    // Next character may be:
-    // * whitespace (followed by either a reserved-body start or
-    //   a '{')
-    // * a '{'
-
-    CHECK_BOUNDS(status);
-
-    if (peek() != LEFT_CURLY_BRACE) {
-        if (!isWhitespace(peek())) {
-            ERROR(status);
-            return;
-        }
-        // Expect a reserved-body start
-        int32_t savedIndex = index;
-        parseRequiredWhitespace(status);
-        CHECK_BOUNDS(status);
-        if (isReservedBodyStart(peek())) {
-            // There is a reserved body
-            Reserved::Builder r(status);
-            builder.setBody(parseReservedBody(r, status));
-        } else {
-            // No body -- backtrack so we can parse 1*([s] expression)
-            index = savedIndex;
-            normalizedInput.truncate(normalizedInput.length() - 1);
-        }
-        // Otherwise, the next character must be a '{'
-        // to open the required expression (or optional whitespace)
-        if (peek() != LEFT_CURLY_BRACE && !isWhitespace(peek())) {
-            ERROR(status);
-            return;
-        }
-    }
-
-    // Finally, parse the expressions
-
-    // Need to look ahead to disambiguate a '{' beginning
-    // an expression from one beginning with a quoted pattern
-    int32_t expressionCount = 0;
-    while (peek() == LEFT_CURLY_BRACE || isWhitespace(peek())) {
-        parseOptionalWhitespace(status);
-
-        bool nextIsLbrace = peek() == LEFT_CURLY_BRACE;
-        bool nextIsQuotedPattern = nextIsLbrace && inBounds(1)
-            && peek(1) == LEFT_CURLY_BRACE;
-        if (nextIsQuotedPattern) {
-            break;
-        }
-
-        builder.addExpression(parseExpression(status), status);
-        expressionCount++;
-    }
-    if (expressionCount <= 0) {
-        // At least one expression is required
-        ERROR(status);
-        return;
-    }
-    dataModel.addUnsupportedStatement(builder.build(status), status);
-}
-
-// Terrible hack to get around the ambiguity between unsupported keywords
-// and supported keywords
-bool Parser::nextIs(const std::u16string_view &keyword) const {
-    for (int32_t i = 0; i < static_cast<int32_t>(keyword.length()); i++) {
-        if (!inBounds(i) || peek(i) != keyword[i]) {
-            return false;
-        }
-    }
-    return true;
-}
-
 /*
   Consume a possibly-empty sequence of declarations separated by whitespace;
   each declaration matches the `declaration` nonterminal in the grammar
@@ -1715,11 +1388,7 @@ void Parser::parseDeclarations(UErrorCode& status) {
 
     while (peek() == PERIOD) {
         CHECK_BOUNDS_1(status);
-        // Check for unsupported statements first
-        // Lookahead is needed to disambiguate keyword from known keywords
-        if (!nextIs(ID_MATCH) && !nextIs(ID_LOCAL) && !nextIs(ID_INPUT)) {
-            parseUnsupportedStatement(status);
-        } else if (peek(1) == ID_LOCAL[1]) {
+        if (peek(1) == ID_LOCAL[1]) {
             parseLocalDeclaration(status);
         } else if (peek(1) == ID_INPUT[1]) {
             parseInputDeclaration(status);
diff --git a/icu4c/source/i18n/messageformat2_parser.h b/icu4c/source/i18n/messageformat2_parser.h
index 4b35760cb118..b62cbe9200b9 100644
--- a/icu4c/source/i18n/messageformat2_parser.h
+++ b/icu4c/source/i18n/messageformat2_parser.h
@@ -127,9 +127,6 @@ namespace message2 {
         void parseOption(OptionAdder<T>&, UErrorCode&);
         template<class T>
         void parseOptions(OptionAdder<T>&, UErrorCode&);
-	void parseReservedChunk(Reserved::Builder&, UErrorCode&);
-	Reserved parseReserved(UErrorCode&);
-        Reserved parseReservedBody(Reserved::Builder&, UErrorCode&);
 	Operator parseAnnotation(UErrorCode&);
 	void parseLiteralOrVariableWithAnnotation(bool, Expression::Builder&, UErrorCode&);
         Markup parseMarkup(UErrorCode&);
diff --git a/icu4c/source/i18n/messageformat2_serializer.cpp b/icu4c/source/i18n/messageformat2_serializer.cpp
index 228cf34181cd..b2765f5acf43 100644
--- a/icu4c/source/i18n/messageformat2_serializer.cpp
+++ b/icu4c/source/i18n/messageformat2_serializer.cpp
@@ -134,36 +134,10 @@ void Serializer::emitAttributes(const OptionMap& attributes) {
     }
 }
 
-void Serializer::emit(const Reserved& reserved) {
-    // Re-escape '\' / '{' / '|' / '}'
-    for (int32_t i = 0; i < reserved.numParts(); i++) {
-        const Literal& l = reserved.getPart(i);
-        if (l.isQuoted()) {
-            emit(l);
-        } else {
-            const UnicodeString& s = l.unquoted();
-            for (int32_t j = 0; j < s.length(); j++) {
-                switch(s[j]) {
-                case LEFT_CURLY_BRACE:
-                case PIPE:
-                case RIGHT_CURLY_BRACE:
-                case BACKSLASH: {
-                    emit(BACKSLASH);
-                    break;
-                }
-                default:
-                    break;
-                }
-                emit(s[j]);
-            }
-        }
-    }
-}
-
  void Serializer::emit(const Expression& expr) {
     emit(LEFT_CURLY_BRACE);
 
-    if (!expr.isReserved() && !expr.isFunctionCall()) {
+    if (!expr.isFunctionCall()) {
         // Literal or variable, no annotation
         emit(expr.getOperand());
     } else {
@@ -176,17 +150,12 @@ void Serializer::emit(const Reserved& reserved) {
         UErrorCode localStatus = U_ZERO_ERROR;
         const Operator* rator = expr.getOperator(localStatus);
         U_ASSERT(U_SUCCESS(localStatus));
-        if (rator->isReserved()) {
-          const Reserved& reserved = rator->asReserved();
-          emit(reserved);
-        } else {
-            emit(COLON);
-            emit(rator->getFunctionName());
-            // No whitespace after function name, in case it has
-            // no options. (when there are options, emit(OptionMap) will
-            // emit the leading whitespace)
-            emit(rator->getOptionsInternal());
-        }
+        emit(COLON);
+        emit(rator->getFunctionName());
+        // No whitespace after function name, in case it has
+        // no options. (when there are options, emit(OptionMap) will
+        // emit the leading whitespace)
+        emit(rator->getOptionsInternal());
     }
     emitAttributes(expr.getAttributesInternal());
     emit(RIGHT_CURLY_BRACE);
@@ -273,26 +242,6 @@ void Serializer::serializeDeclarations() {
     }
 }
 
-void Serializer::serializeUnsupported() {
-    const UnsupportedStatement* statements = dataModel.getUnsupportedStatementsInternal();
-    U_ASSERT(dataModel.unsupportedStatementsLen == 0 || statements != nullptr);
-
-    for (int32_t i = 0; i < dataModel.unsupportedStatementsLen; i++) {
-        const UnsupportedStatement& s = statements[i];
-        emit(s.getKeyword());
-        UErrorCode localErrorCode = U_ZERO_ERROR;
-        const Reserved* r = s.getBody(localErrorCode);
-        if (U_SUCCESS(localErrorCode)) {
-            whitespace();
-            emit(*r);
-        }
-        const Expression* e = s.getExpressionsInternal();
-        for (int32_t j = 0; j < s.expressionsLen; j++) {
-            emit(e[j]);
-        }
-    }
-}
-
 void Serializer::serializeSelectors() {
     U_ASSERT(!dataModel.hasPattern());
     const Expression* selectors = dataModel.getSelectorsInternal();
@@ -319,7 +268,6 @@ void Serializer::serializeVariants() {
 // Main (public) serializer method
 void Serializer::serialize() {
     serializeDeclarations();
-    serializeUnsupported();
     // Pattern message
     if (dataModel.hasPattern()) {
       emit(dataModel.getPattern());
diff --git a/icu4c/source/i18n/messageformat2_serializer.h b/icu4c/source/i18n/messageformat2_serializer.h
index 38d3412665a4..1b97b3b93008 100644
--- a/icu4c/source/i18n/messageformat2_serializer.h
+++ b/icu4c/source/i18n/messageformat2_serializer.h
@@ -44,14 +44,12 @@ namespace message2 {
         void emit(const Key&);
         void emit(const SelectorKeys&);
         void emit(const Operand&);
-        void emit(const Reserved&);
         void emit(const Expression&);
         void emit(const PatternPart&);
         void emit(const Pattern&);
         void emit(const Variant*);
         void emitAttributes(const OptionMap&);
         void emit(const OptionMap&);
-        void serializeUnsupported();
         void serializeDeclarations();
         void serializeSelectors();
         void serializeVariants();
diff --git a/icu4c/source/i18n/unicode/messageformat2_data_model.h b/icu4c/source/i18n/unicode/messageformat2_data_model.h
index 65dc836caeb3..0c836af1bdfd 100644
--- a/icu4c/source/i18n/unicode/messageformat2_data_model.h
+++ b/icu4c/source/i18n/unicode/messageformat2_data_model.h
@@ -62,163 +62,6 @@ namespace message2 {
         class Literal;
         class Operator;
 
-        /**
-         * The `Reserved` class represents a `reserved` annotation, as in the `reserved` nonterminal
-         * in the MessageFormat 2 grammar or the `Reserved` interface
-         * defined in
-         * https://github.com/unicode-org/message-format-wg/blob/main/spec/data-model.md#expressions
-         *
-         * `Reserved` is immutable, copyable and movable.
-         *
-         * @internal ICU 75 technology preview
-         * @deprecated This API is for technology preview only.
-         */
-        class U_I18N_API Reserved : public UMemory {
-        public:
-            /**
-             * A `Reserved` is a sequence of literals.
-             *
-             * @return The number of literals.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            int32_t numParts() const;
-            /**
-             * Indexes into the sequence.
-             * Precondition: i < numParts()
-             *
-             * @param i Index of the part being accessed.
-             * @return A reference to he i'th literal in the sequence
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            const Literal& getPart(int32_t i) const;
-
-            /**
-             * The mutable `Reserved::Builder` class allows the reserved sequence to be
-             * constructed one part at a time.
-             *
-             * Builder is not copyable or movable.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            class U_I18N_API Builder : public UMemory {
-            private:
-                UVector* parts; // Not a LocalPointer for the same reason as in `SelectorKeys::Builder`
-
-            public:
-                /**
-                 * Adds a single literal to the reserved sequence.
-                 *
-                 * @param part The literal to be added. Passed by move.
-                 * @param status Input/output error code
-                 * @return A reference to the builder.
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                Builder& add(Literal&& part, UErrorCode& status) noexcept;
-                /**
-                 * Constructs a new immutable `Reserved` using the list of parts
-                 * set with previous `add()` calls.
-                 *
-                 * The builder object (`this`) can still be used after calling `build()`.
-                 *
-                 * param status Input/output error code
-                 * @return          The new Reserved object
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                Reserved build(UErrorCode& status) const noexcept;
-                /**
-                 * Default constructor.
-                 * Returns a builder with an empty Reserved sequence.
-                 *
-                 * param status Input/output error code
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                Builder(UErrorCode& status);
-                /**
-                 * Destructor.
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                virtual ~Builder();
-                Builder(const Builder&) = delete;
-                Builder& operator=(const Builder&) = delete;
-                Builder(Builder&&) = delete;
-                Builder& operator=(Builder&&) = delete;
-            }; // class Reserved::Builder
-            /**
-             * Non-member swap function.
-             * @param r1 will get r2's contents
-             * @param r2 will get r1's contents
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            friend inline void swap(Reserved& r1, Reserved& r2) noexcept {
-                using std::swap;
-
-                swap(r1.bogus, r2.bogus);
-                swap(r1.parts, r2.parts);
-                swap(r1.len, r2.len);
-            }
-            /**
-             * Copy constructor.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            Reserved(const Reserved& other);
-            /**
-             * Assignment operator
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            Reserved& operator=(Reserved) noexcept;
-            /**
-             * Default constructor.
-             * Puts the Reserved into a valid but undefined state.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            Reserved() { parts = LocalArray<Literal>(); }
-            /**
-             * Destructor.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            virtual ~Reserved();
-        private:
-            friend class Builder;
-            friend class Operator;
-
-            // True if a copy failed; this has to be distinguished
-            // from a valid `Reserved` with empty parts
-            bool bogus = false;
-
-            // Possibly-empty list of parts
-            // `literal` reserved as a quoted literal; `reserved-char` / `reserved-escape`
-            // strings represented as unquoted literals
-            /* const */ LocalArray<Literal> parts;
-            int32_t len = 0;
-
-            Reserved(const UVector& parts, UErrorCode& status) noexcept;
-            // Helper
-            static void initLiterals(Reserved&, const Reserved&);
-        };
-
       /**
          * The `Literal` class corresponds to the `literal` nonterminal in the MessageFormat 2 grammar,
          * https://github.com/unicode-org/message-format-wg/blob/main/spec/message.abnf and the
@@ -349,8 +192,6 @@ namespace message2 {
             virtual ~Literal();
 
         private:
-            friend class Reserved::Builder;
-
             /* const */ bool thisIsQuoted = false;
             /* const */ UnicodeString contents;
         };
@@ -986,60 +827,22 @@ namespace message2 {
         }; // class OptionMap
         #endif
 
-      // Internal use only
-      #ifndef U_IN_DOXYGEN
-      class U_I18N_API Callable : public UObject {
-      public:
-          friend inline void swap(Callable& c1, Callable& c2) noexcept {
-              using std::swap;
-
-              swap(c1.name, c2.name);
-              swap(c1.options, c2.options);
-          }
-          const FunctionName& getName() const { return name; }
-          const OptionMap& getOptions() const { return options; }
-          Callable(const FunctionName& f, const OptionMap& opts) : name(f), options(opts) {}
-          Callable& operator=(Callable) noexcept;
-          Callable(const Callable&);
-          Callable() = default;
-          virtual ~Callable();
-      private:
-          /* const */ FunctionName name;
-          /* const */ OptionMap options;
-      };
-      #endif
   } // namespace data_model
 } // namespace message2
 
 U_NAMESPACE_END
 
-/// @cond DOXYGEN_IGNORE
-// Export an explicit template instantiation of the std::variant that is used as a
-// data member of various MFDataModel classes.
-// (When building DLLs for Windows this is required.)
-// (See measunit_impl.h, datefmt.h, collationiterator.h, erarules.h and others
-// for similar examples.)
-#if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN
-#if defined(U_REAL_MSVC) && defined(_MSVC_STL_VERSION)
-template class U_I18N_API std::_Variant_storage_<false, icu::message2::data_model::Reserved,icu::message2::data_model::Callable>;
-#endif
-template class U_I18N_API std::variant<icu::message2::data_model::Reserved,icu::message2::data_model::Callable>;
-#endif
-/// @endcond
-
 U_NAMESPACE_BEGIN
 
 namespace message2 {
   namespace data_model {
       /**
-         * The `Operator` class corresponds to the `FunctionRef | Reserved` type in the
+         * The `Operator` class corresponds to the `FunctionRef` type in the
          * `Expression` interface defined in
          * https://github.com/unicode-org/message-format-wg/blob/main/spec/data-model.md#patterns
          *
-         * It represents the annotation that an expression can have: either a function name paired
-         * with a map from option names to operands (possibly empty),
-         * or a reserved sequence, which has no meaning and results in an error if the formatter
-         * is invoked.
+         * It represents the annotation that an expression can have: a function name paired
+         * with a map from option names to operands (possibly empty).
          *
          * `Operator` is immutable, copyable and movable.
          *
@@ -1048,18 +851,8 @@ namespace message2 {
          */
         class U_I18N_API Operator : public UObject {
         public:
-            /**
-             * Determines if this operator is a reserved annotation.
-             *
-             * @return true if and only if this operator represents a reserved sequence.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            UBool isReserved() const { return std::holds_alternative<Reserved>(contents); }
             /**
              * Accesses the function name.
-             * Precondition: !isReserved()
              *
              * @return The function name of this operator.
              *
@@ -1067,19 +860,8 @@ namespace message2 {
              * @deprecated This API is for technology preview only.
              */
             const FunctionName& getFunctionName() const;
-            /**
-             * Accesses the underlying reserved sequence.
-             * Precondition: isReserved()
-             *
-             * @return The reserved sequence represented by this operator.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            const Reserved& asReserved() const;
             /**
              * Accesses function options.
-             * Precondition: !isReserved()
              *
              * @return A vector of function options for this operator.
              *
@@ -1087,11 +869,7 @@ namespace message2 {
              * @deprecated This API is for technology preview only.
              */
             std::vector<Option> getOptions() const {
-                const Callable* f = std::get_if<Callable>(&contents);
-                // This case should never happen, as the precondition is !isReserved()
-                if (f == nullptr) { return {}; }
-                const OptionMap& opts = f->getOptions();
-                return opts.getOptions();
+                return options.getOptions();
             }
             /**
              * The mutable `Operator::Builder` class allows the operator to be constructed
@@ -1105,30 +883,12 @@ namespace message2 {
             class U_I18N_API Builder : public UMemory {
             private:
                 friend class Operator;
-                bool isReservedSequence = false;
-                bool hasFunctionName = false;
-                bool hasOptions = false;
-                Reserved asReserved;
                 FunctionName functionName;
                 OptionMap::Builder options;
             public:
-                /**
-                 * Sets this operator to be a reserved sequence.
-                 * If a function name and/or options were previously set,
-                 * clears them.
-                 *
-                 * @param reserved The reserved sequence to set as the contents of this Operator.
-                 *                 (Passed by move.)
-                 * @return A reference to the builder.
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                Builder& setReserved(Reserved&& reserved);
                 /**
                  * Sets this operator to be a function annotation and sets its name
                  * to `func`.
-                 * If a reserved sequence was previously set, clears it.
                  *
                  * @param func The function name.
                  * @return A reference to the builder.
@@ -1140,7 +900,6 @@ namespace message2 {
                 /**
                  * Sets this operator to be a function annotation and adds a
                  * single option.
-                 * If a reserved sequence was previously set, clears it.
                  *
                  * @param key The name of the option.
                  * @param value The value (right-hand side) of the option.
@@ -1152,10 +911,8 @@ namespace message2 {
                  */
                 Builder& addOption(const UnicodeString &key, Operand&& value, UErrorCode& status) noexcept;
                 /**
-                 * Constructs a new immutable `Operator` using the `reserved` annotation
-                 * or the function name and options that were previously set.
-                 * If neither `setReserved()` nor `setFunctionName()` was previously
-                 * called, then `status` is set to U_INVALID_STATE_ERROR.
+                 * Constructs a new immutable `Operator` using the
+                 * function name and options that were previously set.
                  *
                  * The builder object (`this`) can still be used after calling `build()`.
                  *
@@ -1171,7 +928,7 @@ namespace message2 {
                 Operator build(UErrorCode& status);
                 /**
                  * Default constructor.
-                 * Returns a Builder with no function name or reserved sequence set.
+                 * Returns a Builder with no function name or options set.
                  *
                  * @param status    Input/output error code.
                  *
@@ -1209,7 +966,8 @@ namespace message2 {
             friend inline void swap(Operator& o1, Operator& o2) noexcept {
                 using std::swap;
 
-                swap(o1.contents, o2.contents);
+                swap(o1.name, o2.name);
+                swap(o1.options, o2.options);
             }
             /**
              * Assignment operator.
@@ -1225,7 +983,7 @@ namespace message2 {
              * @internal ICU 75 technology preview
              * @deprecated This API is for technology preview only.
              */
-            Operator() : contents(Reserved()) {}
+            Operator() {}
             /**
              * Destructor.
              *
@@ -1242,12 +1000,12 @@ namespace message2 {
 
             // Function call constructor
             Operator(const FunctionName& f, const UVector& options, UErrorCode&);
-            // Reserved sequence constructor
-            Operator(const Reserved& r) : contents(r) {}
 
             const OptionMap& getOptionsInternal() const;
             Operator(const FunctionName&, const OptionMap&);
-            /* const */ std::variant<Reserved, Callable> contents;
+
+            /* const */ FunctionName name;
+            /* const */ OptionMap options;
         }; // class Operator
   } // namespace data_model
 } // namespace message2
@@ -1262,7 +1020,6 @@ U_NAMESPACE_END
 // for similar examples.)
 #if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN
 template class U_I18N_API std::optional<icu::message2::data_model::Operator>;
-template class U_I18N_API std::optional<icu::message2::data_model::Reserved>;
 #endif
 /// @endcond
 
@@ -1520,8 +1277,7 @@ namespace message2 {
             UBool isStandaloneAnnotation() const;
             /**
              * Checks if this expression has a function
-             * annotation (with or without an operand). A reserved
-             * sequence is not a function annotation.
+             * annotation (with or without an operand).
              *
              * @return True if and only if the expression has an annotation
              *         that is a function.
@@ -1531,20 +1287,9 @@ namespace message2 {
              */
             UBool isFunctionCall() const;
             /**
-             * Returns true if and only if this expression is
-             * annotated with a reserved sequence.
-             *
-             * @return True if and only if the expression has an
-             *         annotation that is a reserved sequence,
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            UBool isReserved() const;
-            /**
-             * Accesses the function or reserved sequence
+             * Accesses the function
              * annotating this expression.
-             * If !(isFunctionCall() || isReserved()), sets
+             * If !(isFunctionCall()), sets
              * `status` to U_INVALID_STATE_ERROR.
              *
              * @param status Input/output error code.
@@ -1751,203 +1496,6 @@ template class U_I18N_API LocalArray<message2::data_model::Expression>;
 
 namespace message2 {
   namespace data_model {
-      /**
-         * The `UnsupportedStatement` class corresponds to the `reserved-statement` nonterminal in the MessageFormat 2
-         * grammar and the `unsupported-statement` type defined in:
-         * https://github.com/unicode-org/message-format-wg/blob/main/spec/data-model/message.json#L169
-         *
-         * It represents a keyword (string) together with an optional
-         * `Reserved` annotation and a non-empty list of expressions.
-         *
-         * `UnsupportedStatement` is immutable, copyable and movable.
-         *
-         * @internal ICU 75 technology preview
-         * @deprecated This API is for technology preview only.
-         */
-        class U_I18N_API UnsupportedStatement : public UObject {
-        public:
-            /**
-             * Accesses the keyword of this statement.
-             *
-             * @return A reference to a string.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            const UnicodeString& getKeyword() const { return keyword; }
-            /**
-             * Accesses the `reserved-body` of this statement.
-             *
-             * @param status Input/output error code. Set to U_ILLEGAL_ARGUMENT_ERROR
-             *         if this unsupported statement has no body.
-             * @return A non-owned pointer to a `Reserved` annotation,
-             *         which is non-null if U_SUCCESS(status).
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            const Reserved* getBody(UErrorCode& status) const;
-            /**
-             * Accesses the expressions of this statement.
-             *
-             * @return A vector of Expressions.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            std::vector<Expression> getExpressions() const {
-                if (expressionsLen <= 0 || !expressions.isValid()) {
-                    // This case should never happen, but we can't use an assertion here
-                    return {};
-                }
-                return toStdVector<Expression>(expressions.getAlias(), expressionsLen);
-            }
-            /**
-             * The mutable `UnsupportedStatement::Builder` class allows the statement to be constructed
-             * incrementally.
-             *
-             * Builder is not copyable or movable.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            class U_I18N_API Builder : public UMemory {
-            private:
-                friend class UnsupportedStatement;
-                friend class message2::Parser;
-
-                UnicodeString keyword;
-                std::optional<Reserved> body;
-                UVector* expressions; // Vector of expressions;
-                                      // not a LocalPointer for
-                                      // the same reason as in `SelectorKeys::builder`
-            public:
-                /**
-                 * Sets the keyword of this statement.
-                 *
-                 * @param k The keyword to set.
-                 * @return A reference to the builder.
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                Builder& setKeyword(const UnicodeString& k);
-                /**
-                 * Sets the body of this statement.
-                 *
-                 * @param r The `Reserved` annotation to set as the body. Passed by move.
-                 * @return A reference to the builder.
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                Builder& setBody(Reserved&& r);
-                /**
-                 * Adds an expression to this statement.
-                 *
-                 * @param e The expression to add. Passed by move.
-                 * @param status Input/output error code.
-                 * @return A reference to the builder.
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                Builder& addExpression(Expression&& e, UErrorCode& status);
-                /**
-                 * Constructs a new immutable `UnsupportedStatement` using the keyword,
-                 * body and (if applicable) expressions that were previously set.
-                 * If `setKeyword()` was never called, then `status` is set to
-                 * U_INVALID_STATE_ERROR. If `setBody()` was never called, the body is
-                 * treated as absent (not an error). If `addExpression()` was not called
-                 * at least once, then `status` is set to U_INVALID_STATE_ERROR.
-                 *
-                 * The builder object (`this`) can still be used after calling `build()`.
-                 * @param status    Input/output error code.
-                 * @return          The new UnsupportedStatement
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                UnsupportedStatement build(UErrorCode& status) const;
-                /**
-                 * Default constructor.
-                 * Returns a Builder with no keyword or body set.
-                 *
-                 * @param status    Input/output error code.
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                Builder(UErrorCode& status);
-                /**
-                 * Destructor.
-                 *
-                 * @internal ICU 75 technology preview
-                 * @deprecated This API is for technology preview only.
-                 */
-                virtual ~Builder();
-                Builder(const Builder&) = delete;
-                Builder& operator=(const Builder&) = delete;
-                Builder(Builder&&) = delete;
-                Builder& operator=(Builder&&) = delete;
-            }; // class UnsupportedStatement::Builder
-            /**
-             * Non-member swap function.
-             * @param s1 will get s2's contents
-             * @param s2 will get s1's contents
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            friend inline void swap(UnsupportedStatement& s1, UnsupportedStatement& s2) noexcept {
-                using std::swap;
-
-                swap(s1.keyword, s2.keyword);
-                swap(s1.body, s2.body);
-                swap(s1.expressions, s2.expressions);
-                swap(s1.expressionsLen, s2.expressionsLen);
-            }
-            /**
-             * Copy constructor.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            UnsupportedStatement(const UnsupportedStatement& other);
-            /**
-             * Assignment operator.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            UnsupportedStatement& operator=(UnsupportedStatement) noexcept;
-            /**
-             * Default constructor.
-             * Puts the UnsupportedStatement into a valid but undefined state.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            UnsupportedStatement() : expressions(LocalArray<Expression>()) {}
-            /**
-             * Destructor.
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            virtual ~UnsupportedStatement();
-        private:
-            friend class message2::Serializer;
-
-            /* const */ UnicodeString keyword;
-            /* const */ std::optional<Reserved> body;
-            /* const */ LocalArray<Expression> expressions;
-            /* const */ int32_t expressionsLen = 0;
-
-            const Expression* getExpressionsInternal() const { return expressions.getAlias(); }
-
-            UnsupportedStatement(const UnicodeString&, const std::optional<Reserved>&, const UVector&, UErrorCode&);
-        }; // class UnsupportedStatement
 
       class Pattern;
 
@@ -2110,8 +1658,6 @@ namespace message2 {
 #if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN
 template class U_I18N_API LocalPointerBase<message2::data_model::PatternPart>;
 template class U_I18N_API LocalArray<message2::data_model::PatternPart>;
-template class U_I18N_API LocalPointerBase<message2::data_model::UnsupportedStatement>;
-template class U_I18N_API LocalArray<message2::data_model::UnsupportedStatement>;
 #endif
 /// @endcond
 
@@ -2599,7 +2145,7 @@ namespace message2 {
             // If non-null, the referent is a member of `expr` so
             // its lifetime is the same as the lifetime of the enclosing Binding
             // (as long as there's no mutation)
-            const std::variant<Reserved, Callable>* annotation = nullptr;
+            const Operator* annotation = nullptr;
 
             const OptionMap& getOptionsInternal() const;
 
@@ -2808,21 +2354,6 @@ namespace message2 {
             return toStdVector<Variant>(match->variants.getAlias(), match->numVariants);
             return {};
         }
-        /**
-         * Accesses the unsupported statements for this data model.
-         *
-         * @return A vector of unsupported statements.
-         *
-         * @internal ICU 75 technology preview
-         * @deprecated This API is for technology preview only.
-         */
-        std::vector<UnsupportedStatement> getUnsupportedStatements() const {
-            std::vector<UnsupportedStatement> result;
-            if (!bogus) {
-                return toStdVector<UnsupportedStatement>(unsupportedStatements.getAlias(), unsupportedStatementsLen);
-            }
-            return {};
-        }
         /**
          * Accesses the pattern (in a message without selectors).
          * Returns a reference to an empty pattern if the message has selectors.
@@ -2873,8 +2404,6 @@ namespace message2 {
             swap(m1.body, m2.body);
             swap(m1.bindings, m2.bindings);
             swap(m1.bindingsLen, m2.bindingsLen);
-            swap(m1.unsupportedStatements, m2.unsupportedStatements);
-            swap(m1.unsupportedStatementsLen, m2.unsupportedStatementsLen);
         }
         /**
          * Assignment operator
@@ -2918,7 +2447,6 @@ namespace message2 {
             UVector* selectors = nullptr;
             UVector* variants = nullptr;
             UVector* bindings = nullptr;
-            UVector* unsupportedStatements = nullptr;
         public:
             /**
              * Adds a binding, There must not already be a binding
@@ -2933,17 +2461,6 @@ namespace message2 {
              * @deprecated This API is for technology preview only.
              */
             Builder& addBinding(Binding&& b, UErrorCode& status);
-            /**
-             * Adds an unsupported statement.
-             *
-             * @param s The statement. Passed by move.
-             * @param status Input/output error code.
-             *
-             *
-             * @internal ICU 75 technology preview
-             * @deprecated This API is for technology preview only.
-             */
-            Builder& addUnsupportedStatement(UnsupportedStatement&& s, UErrorCode& status);
             /**
              * Adds a selector expression. Copies `expression`.
              * If a pattern was previously set, clears the pattern.
@@ -3046,16 +2563,9 @@ namespace message2 {
         /* const */ LocalArray<Binding> bindings;
         int32_t bindingsLen = 0;
 
-        // Unsupported statements
-        // (Treated as a type of `declaration` in the data model spec;
-        // stored separately for convenience)
-        /* const */ LocalArray<UnsupportedStatement> unsupportedStatements;
-        int32_t unsupportedStatementsLen = 0;
-
         const Binding* getLocalVariablesInternal() const;
         const Expression* getSelectorsInternal() const;
         const Variant* getVariantsInternal() const;
-        const UnsupportedStatement* getUnsupportedStatementsInternal() const;
 
         int32_t numSelectors() const {
             const Matcher* matcher = std::get_if<Matcher>(&body);
diff --git a/icu4c/source/test/intltest/messageformat2test_read_json.cpp b/icu4c/source/test/intltest/messageformat2test_read_json.cpp
index 53d25ebe715c..ddf93da632ce 100644
--- a/icu4c/source/test/intltest/messageformat2test_read_json.cpp
+++ b/icu4c/source/test/intltest/messageformat2test_read_json.cpp
@@ -34,9 +34,6 @@ static UErrorCode getExpectedRuntimeErrorFromString(const std::string& errorName
     if (errorName == "unresolved-variable") {
         return U_MF_UNRESOLVED_VARIABLE_ERROR;
     }
-    if (errorName == "unsupported-expression") {
-        return U_MF_UNSUPPORTED_EXPRESSION_ERROR;
-    }
     if (errorName == "bad-operand") {
         return U_MF_OPERAND_MISMATCH_ERROR;
     }
@@ -58,11 +55,8 @@ static UErrorCode getExpectedRuntimeErrorFromString(const std::string& errorName
     if (errorName == "bad-selector") {
         return U_MF_SELECTOR_ERROR;
     }
-    if (errorName == "formatting-error") {
-        return U_MF_FORMATTING_ERROR;
-    }
 // Arbitrary default
-    return U_MF_UNSUPPORTED_STATEMENT_ERROR;
+    return U_MF_FORMATTING_ERROR;
 }
 
 static UnicodeString u_str(std::string s) {
@@ -295,17 +289,14 @@ void TestMessageFormat2::jsonTestsFromFiles(IcuTestErrorCode& errorCode) {
 
     // Do spec tests for syntax errors
     runTestsFromJsonFile(*this, "spec/syntax-errors.json", errorCode);
+    runTestsFromJsonFile(*this, "unsupported-expressions.json", errorCode);
+    runTestsFromJsonFile(*this, "unsupported-statements.json", errorCode);
+    runTestsFromJsonFile(*this, "syntax-errors-reserved.json", errorCode);
 
     // Do tests for data model errors
     runTestsFromJsonFile(*this, "spec/data-model-errors.json", errorCode);
     runTestsFromJsonFile(*this, "more-data-model-errors.json", errorCode);
 
-    // Do tests for reserved statements/expressions
-    runTestsFromJsonFile(*this, "spec/unsupported-expressions.json", errorCode);
-    runTestsFromJsonFile(*this, "spec/unsupported-statements.json", errorCode);
-    // Uncomment when reserved syntax is removed
-    // runTestsFromJsonFile(*this, "syntax-errors-reserved.json", errorCode);
-
     // Do valid spec tests
     runTestsFromJsonFile(*this, "spec/syntax.json", errorCode);
 
diff --git a/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/message2/CoreTest.java b/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/message2/CoreTest.java
index dd2698087be8..63e3eefddf1d 100644
--- a/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/message2/CoreTest.java
+++ b/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/message2/CoreTest.java
@@ -42,6 +42,8 @@ public class CoreTest extends CoreTestFmwk {
                                                 "syntax-errors-end-of-input.json",
                                                 "syntax-errors-reserved.json",
                                                 "tricky-declarations.json",
+                                                "unsupported-expressions.json",
+                                                "unsupported-statements.json",
                                                 "valid-tests.json"};
 
     @Test
diff --git a/testdata/message2/more-data-model-errors.json b/testdata/message2/more-data-model-errors.json
index 14c33c66d353..32744083af1c 100644
--- a/testdata/message2/more-data-model-errors.json
+++ b/testdata/message2/more-data-model-errors.json
@@ -102,34 +102,6 @@
         }
       ]
     },
-
-    {
-      "src": ".match {|horse| ^private}\n   1 {{The value is one.}}   * {{The value is not one.}}",
-      "expErrors": [
-        {
-          "type": "missing-selector-annotation"
-        }
-      ]
-    },
-
-    {
-      "src": ".match {$foo !select}  |1| {{one}}  * {{other}}",
-      "expErrors": [
-        {
-          "type": "missing-selector-annotation"
-        }
-      ]
-    },
-
-    {
-      "src": ".match {$foo ^select}  |1| {{one}}  * {{other}}",
-      "expErrors": [
-        {
-          "type": "missing-selector-annotation"
-        }
-      ]
-    },
-
     {
       "src": ".input {$foo} .match {$foo} one {{one}} * {{other}}",
       "expErrors": [
diff --git a/testdata/message2/resolution-errors.json b/testdata/message2/resolution-errors.json
index 610588e0cf5e..8f1ac2fb9364 100644
--- a/testdata/message2/resolution-errors.json
+++ b/testdata/message2/resolution-errors.json
@@ -9,13 +9,6 @@
     { "src": ".input {$x :number} {{{$x}}}", "exp": "{$x}", "expErrors": [{ "type": "unresolved-variable" }], "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"},
     { "src": ".local $foo = {$bar} .match {$foo :number}  one {{one}}  * {{other}}", "exp": "other", "expErrors": [{ "type": "unresolved-variable" }], "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"},
     { "src": ".local $bar = {$none :number} .match {$foo :string}  one {{one}}  * {{{$bar}}}", "exp": "{$none}", "expErrors": [{ "type": "unresolved-variable" }], "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"},
-    { "src": "The value is {horse :func}.", "exp": "The value is {|horse|}.", "expErrors": [{ "type": "unknown-function" }], "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"},
-    { "src": ".matc {-1} {{hello}}",
-      "expErrors": [{ "type": "unsupported-statement" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    { "src": ".m {-1} {{hello}}",
-      "expErrors": [{ "type": "unsupported-statement" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782" }
+    { "src": "The value is {horse :func}.", "exp": "The value is {|horse|}.", "expErrors": [{ "type": "unknown-function" }], "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"}
   ]
 }
diff --git a/testdata/message2/spec/syntax.json b/testdata/message2/spec/syntax.json
index 1b901eb639d7..558fc64062b4 100644
--- a/testdata/message2/spec/syntax.json
+++ b/testdata/message2/spec/syntax.json
@@ -172,13 +172,6 @@
       "src": ".local $x ={a}.input{$y}{{}}",
       "exp": ""
     },
-    {
-      "description": "message -> complex-message -> *(declaration [s]) complex-body -> declaration complex-body -> reserved-statement  complex-body -> reserved-keyword expression -> \".\" name expression complex-body",
-      "src": ".n{a}{{}}",
-      "exp": "",
-      "expErrors": [ { "type": "unsupported-statement" } ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
     {
       "description": "message -> complex-message -> complex-body -> matcher -> match-statement variant -> match selector key quoted-pattern -> \".match\" expression literal quoted-pattern",
       "src": ".match{a :f}a{{}}*{{}}",
@@ -298,20 +291,6 @@
       "expErrors": [{ "type": "unknown-function" }],
       "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
     },
-    {
-      "description": "... annotation -> private-use-annotation -> private-start",
-      "src": "{^}",
-      "exp": "{^}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... annotation -> reserved-annotation -> reserved-annotation-start",
-      "src": "{!}",
-      "exp": "{!}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
     {
       "description": "message -> simple-message -> simple-start pattern -> placeholder -> markup -> \"{\" s \"#\" identifier \"}\"", 
       "src": "{ #a}",
@@ -507,132 +486,6 @@
       "src": "{0E-1}",
       "exp": "0E-1"
     },
-    {
-      "description": "... reserved-statement -> reserved-keyword s reserved-body 1*([s] expression) -> reserved-keyword s reserved-body expression -> \".\" name s reserved-body-part expression -> \".\" name s reserved-char expression ...",
-      "src": ".n .{a}{{}}",
-      "exp": "",
-      "expErrors": [ { "type": "unsupported-statement" } ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-statement -> reserved-keyword reserved-body 1*([s] expression) -> reserved-keyword s reserved-body s expression -> \".\" name s reserved-body-part expression -> \".\" name s reserved-char expression ...",
-      "src": ".n. {a}{{}}",
-      "exp": "",
-      "expErrors": [ { "type": "unsupported-statement" } ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-statement -> reserved-keyword reserved-body 1*([s] expression) -> reserved-keyword reserved-body expression expression -> \".\" name reserved-body-part expression expression -> \".\" name s reserved-char expression expression ...",
-      "src": ".n.{a}{b}{{}}",
-      "exp": "",
-      "expErrors": [ { "type": "unsupported-statement" } ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation -> reserved-annotation-start reserved-body -> \"!\" reserved-body-part -> \"!\" reserved-char ...",
-      "src": "{!.}",
-      "exp": "{!}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation -> reserved-annotation-start s reserved-body -> \"!\" s reserved-body-part -> \"!\" s reserved-char ...",
-      "src": "{! .}",
-      "exp": "{!}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation-start ...",
-      "src": "{%}",
-      "exp": "{%}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation-start ...",
-      "src": "{*}",
-      "exp": "{*}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation-start ...",
-      "src": "{+}",
-      "exp": "{+}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation-start ...",
-      "src": "{<}",
-      "exp": "{<}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation-start ...",
-      "src": "{>}",
-      "exp": "{>}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation-start ...",
-      "src": "{?}",
-      "exp": "{?}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation-start ...",
-      "src": "{~}",
-      "exp": "{~}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... private-use-annotation -> private-start reserved-body -> \"^\" reserved-body-part -> \"^\" reserved-char ...",
-      "src": "{^.}",
-      "exp": "{^}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... private-use-annotation -> private-start s reserved-body -> \"^\" s reserved-body-part -> \"^\" s reserved-char ...",
-      "src": "{^ .}",
-      "exp": "{^}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... private-start ...",
-      "src": "{&}",
-      "exp": "{&}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation -> reserved-annotation-start reserved-body -> \"!\" reserved-body-part reserved-body-part -> \"!\" reserved-char escaped-char ...",
-      "src": "{!.\\{}",
-      "exp": "{!}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation -> reserved-annotation-start reserved-body -> \"!\" reserved-body-part s reserved-body-part -> \"!\" reserved-char s escaped-char ...",
-      "src": "{!. \\{}",
-      "exp": "{!}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "description": "... reserved-annotation -> reserved-annotation-start reserved-body -> \"!\" reserved-body-part -> \"!\" quoted-literal ...",
-      "src": "{!|a|}",
-      "exp": "{!}",
-      "expErrors": [{ "type": "unsupported-expression" }],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
     {
       "src": "hello { world\t\n}",
       "exp": "hello world"
@@ -838,130 +691,6 @@
         }
       ]
     },
-    {
-      "src": "foo {+reserved}",
-      "exp": "foo {+}",
-      "expParts": [
-        {
-          "type": "literal",
-          "value": "foo "
-        },
-        {
-          "type": "fallback",
-          "source": "+"
-        }
-      ],
-      "expErrors": [
-        {
-          "type": "unsupported-expression"
-        }
-      ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "src": "foo {&private}",
-      "exp": "foo {&}",
-      "expParts": [
-        {
-          "type": "literal",
-          "value": "foo "
-        },
-        {
-          "type": "fallback",
-          "source": "&"
-        }
-      ],
-      "expErrors": [
-        {
-          "type": "unsupported-expression"
-        }
-      ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "src": "foo {?reserved @a @b=$c}",
-      "exp": "foo {?}",
-      "expParts": [
-        {
-          "type": "literal",
-          "value": "foo "
-        },
-        {
-          "type": "fallback",
-          "source": "?"
-        }
-      ],
-      "expErrors": [
-        {
-          "type": "unsupported-expression"
-        }
-      ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "src": ".foo {42} {{bar}}",
-      "exp": "bar",
-      "expParts": [
-        {
-          "type": "literal",
-          "value": "bar"
-        }
-      ],
-      "expErrors": [
-        {
-          "type": "unsupported-statement"
-        }
-      ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "src": ".foo{42}{{bar}}",
-      "exp": "bar",
-      "expParts": [
-        {
-          "type": "literal",
-          "value": "bar"
-        }
-      ],
-      "expErrors": [
-        {
-          "type": "unsupported-statement"
-        }
-      ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "src": ".foo |}lit{| {42}{{bar}}",
-      "exp": "bar",
-      "expParts": [
-        {
-          "type": "literal",
-          "value": "bar"
-        }
-      ],
-      "expErrors": [
-        {
-          "type": "unsupported-statement"
-        }
-      ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
-    {
-      "src": ".l $y = {|bar|} {{}}",
-      "exp": "",
-      "expParts": [
-        {
-          "type": "literal",
-          "value": "bar"
-        }
-      ],
-      "expErrors": [
-        {
-          "type": "unsupported-statement"
-        }
-      ],
-      "ignoreJava": "See https://github.com/unicode-org/message-format-wg/issues/782"
-    },
     {
       "src": "{{trailing whitespace}} \n",
       "exp": "trailing whitespace"
diff --git a/testdata/message2/spec/unsupported-statements.json b/testdata/message2/spec/unsupported-statements.json
deleted file mode 100644
index d944aa0f786d..000000000000
--- a/testdata/message2/spec/unsupported-statements.json
+++ /dev/null
@@ -1,18 +0,0 @@
-{
-  "scenario": "Reserved statements",
-  "description": "Tests for unsupported statements",
-  "defaultTestProperties": {
-    "locale": "en-US",
-    "expErrors": [
-      {
-        "type": "unsupported-statement"
-      }
-    ]
-  },
-  "tests": [
-    { "src" : ".i {1} {{}}" },
-    { "src" : ".l $y = {|bar|} {{}}" },
-    { "src" : ".l $x.y = {|bar|} {{}}" }
-  ]
-}
-
diff --git a/testdata/message2/spec/unsupported-expressions.json b/testdata/message2/unsupported-expressions.json
similarity index 67%
rename from testdata/message2/spec/unsupported-expressions.json
rename to testdata/message2/unsupported-expressions.json
index f7d611509d23..7e9a64943bd1 100644
--- a/testdata/message2/spec/unsupported-expressions.json
+++ b/testdata/message2/unsupported-expressions.json
@@ -1,11 +1,11 @@
 {
   "scenario": "Reserved and private annotations",
-  "description": "Tests for unsupported expressions (reserved/private)",
+  "description": "Tests for unsupported expressions (reserved/private) (now syntax errors)",
   "defaultTestProperties": {
     "locale": "en-US",
     "expErrors": [
       {
-        "type": "unsupported-expression"
+        "type": "syntax-error"
       }
     ]
   },
@@ -47,7 +47,31 @@
     { "src": "hello {$foo    +num x \\\\ abcde |3.14| r  }"  },
     { "src": "hello {$foo    >num x \\\\ abcde |aaa||3.14||42| r  }"  },
     { "src": "hello {$foo    >num x \\\\ abcde |aaa||3.14| |42| r  }"  },
-    { "src" : ".input{ $n ~ }{{{$n}}}" }
+    { "src" : ".input{ $n ~ }{{{$n}}}" },
+    { "src":  "foo {+reserved}"},
+    { "src": "foo {&private}" },
+    { "src": "foo {?reserved @a @b=$c}" },
+    { "src": "{!.}" },
+    { "src": "{! .}" },
+    { "src": "{%}" },
+    { "src": "{*}" },
+    { "src": "{+}" },
+    { "src": "{<}" },
+    { "src": "{>}" },
+    { "src": "{?}" },
+    { "src": "{~}" },
+    { "src": "{^.}" },
+    { "src": "{^ .}" },
+    { "src": "{&}" },
+    { "src": "{!.\\{}" },
+    { "src": "{!. \\{}" },
+    { "src": "{!|a|}" },
+    { "src": "{^}" },
+    { "src": "{!}" },
+    { "src": ".match {$foo !select}  |1| {{one}}  * {{other}}" },
+    { "src": ".match {$foo ^select}  |1| {{one}}  * {{other}}" },
+    { "src": ".match {|horse| ^private}\n   1 {{The value is one.}}   * {{The value is not one.}}" },
+    { "src": ".match {$foo ^select}  |1| {{one}}  * {{other}}" }
   ]
 }
 
diff --git a/testdata/message2/unsupported-statements.json b/testdata/message2/unsupported-statements.json
new file mode 100644
index 000000000000..46cf75ac1e99
--- /dev/null
+++ b/testdata/message2/unsupported-statements.json
@@ -0,0 +1,27 @@
+{
+  "scenario": "Reserved statements",
+  "description": "Tests for unsupported statements (now syntax errors)",
+  "defaultTestProperties": {
+    "locale": "en-US",
+    "expErrors": [
+      {
+        "type": "syntax-error"
+      }
+    ]
+  },
+  "tests": [
+    { "src" : ".i {1} {{}}" },
+    { "src" : ".l $y = {|bar|} {{}}" },
+    { "src" : ".l $x.y = {|bar|} {{}}" },
+    { "src": ".matc {-1} {{hello}}" },
+    { "src": ".m {-1} {{hello}}" },
+    { "src": ".n{a}{{}}" },
+    { "src": ".foo {42} {{bar}}" },
+    { "src": ".foo{42}{{bar}}" },
+    { "src": ".foo |}lit{| {42}{{bar}}" },
+    { "src": ".n .{a}{{}}" },
+    { "src": ".n. {a}{{}}" },
+    { "src": ".n.{a}{b}{{}}" }
+  ]
+}
+