ORA-00201: control file version 12.1.0.2.0 incompatible with ORACLE version 11.2.0.0.0
(I accept that this is not quite technically accurate, but is close enough)

The error message is telling you that the database was created in a higher version than the one you are trying to open it in.  All the database files are marked with this version.

This database was created in v12, you're trying to open it in v11.  This will not work.  There is nothing you can do except use a v12 database home to mount/open the database.

It is possible to create a database in v12 which is compatible with v11, by using the COMPATIBLE parameter.  This tells the database engine what version the database should remain compatible with, and what database features to use.