So let's say I capture En Passant with a pawn, using that same pawn I get to the 8th rank. Can I promote that pawn into anything else? I've heard of this restriction in various ways. Some say it can become a rook at best, some say it just stays a pawn, but moves backwards.
Please let me know if this is a classic case of "I'm losing better make some stuff up." Or an actual rule.