A) NO, you have to insert this save on PS5 and import it from the game (PS5 version)
B) NO but it will surely ask you to overwrite previous saves. I advise you to make a copy on the Cloud with synchronization disabled.
C) NO
As written everywhere, some trophies are glitched, so you may have trouble unlocking them. For some it worked the autopop, for others it left some trophy stuck.