Can I downgrade or upgrade from Cubase 12AI to Cubase 11pro??
No. The new licensing system will prevent that.
You would need a USB-eLicenser for Cubase 11 pro.
Maybe the easiest way is to find someone selling a Cubase 11 Pro license (but beware, if that license was used to upgrade to 12 or 13, you will never be able to upgrade it again to a future version).
He will not be able to use it if it was upgraded.
These licenses are not transferable. Because they are upgraded already.
And as far as I know, it is possible, but the seller would surrender his version 12 license too (buyer would receive 11 and 12 at the same time). Check this topic:
It is so much helpful, thank you very much.