If:

• Database actual version is 12 AND
• Compatibility level is set to V11R1

Then this is equivalent to the lowest level outlined in the function level list which is V12R1M100 (which could also be the value returned from the query that checks the level)

For the purpose of whether to use the offset keyword or not, that is enabled in V12R1M500 (mentioned here https://www.ibm.com/docs/en/db2-for-zos/12?topic=12-sql-changes-in-db2, which might also be helpful in determining when other features are turned on in which function level).