There is a 64-byte block of flash called metadata section which is the shared area for both bootloader and bootloadable applications. It contains various fields such as Bootloadable Application Custom ID, Bootloadable Application ID etc., If compatibility is checked via application version or ID, the user can use these medadata fields straight away. These fields contain the application details specified in the bootloadable Component customizer.
Bootloader supports uint32 Bootloader_GetMetadata (uint8 field, uint8 appId) API that returns the value of the specified metadata field. This can be checked for compatibility and launch/bootload appropriate bootloadable firmware from bootloader.