FILE_SCHEMA vs. Schema Version

Hello all, we faced some difficulties to import IFC4 files. The FILE_SCHEMA tag indicated IFC4
FILE_SCHEMA((‘IFC4’), but finally it contains data based on Schema version 4.0.2, IFC4 Add2, with some new items. As we are using a generative importer to make sure the schema is correct, we like to know the real schema content of a file and not only the major version. Version 4 already has a lot of addendum and extensions. So I like to know how to judge the correct Schema Version of an IFC4 file.

Maybe there is already a clear definition I to identify the correct schema version. Just refer to the ifs-schema-specifications page (not allowed to add a link to the buildingsmart side)

Every hint welcome. Thanks a lot.