What does val age: Int by values guarantee when values has type Map<String, Any?>?

What does val age: Int by values guarantee when values has type Map<String, Any?>?

1. Only that reads use the key "age"; key presence and runtime value type can still fail
2. The compiler inserts age with a default value of zero when it is missing
3. Every Number value is automatically converted to Int
4. Renaming the property also migrates persisted map keys