While the Generic Remotes will be going away, they aren’t gone yet. When I migrated from 11 the Generic Remotes for METAGRID did not follow. But if you create new Generic Remotes and Import the settings files (.xml) that you used in Cubase 11 it works just like before.
If you don’t recall where those setup files can be found - launch Cubase 11 and Export them to a known location.
Probably. I got METAGRID fairly early and the remotes were a bit different then. By the time they setup the current remote scheme I’d done some major editing on my remote setups so I just continued down that path rather than switching (and re-editing).