What content do I need to reinstall?

Hello. I am upgrading from Cubase 11 to Cubase 12. Do I have to reinstall all Steinberg instruments (ie retrologue, halion se, groove agent) and Steinberg audio/midi content (ie EDM elements, groove agent kits, halion se samples, hip hop loops, etc) or will it still be there due to previous Cubase 11 install? And if it will still be there, will it all disappear if I delete cubase 11? thanks

Yes it will still be there. No deleting Cubase does not remove the content. You can use the Steinberg Library Manager to relocate existing content and register new content if needed.