We know nothing whatever about the thief on the cross and no, we can't theorize that he'd been baptized. We don't know where he was from or exactly what his crime was. He did say that he deserved death. We know nothing except that he repented on the cross and Jesus saved him, right then and there. If he'd been baptized, it was before his salvation so it was meaningless.

Yes, Cornelius and his family got baptized, but AFTER they were filled with the spirit. Read the order of events. Peter saw that they had received the Holy Spirit and then questioned whether it was ok to baptize gentiles. He decided that since they'd been saved and since they'd been filled with the Spirit, then baptism was ok. They were very clearly saved without baptism.

“In a time of deceit telling the truth is a revolutionary act.”
― George Orwell

It's not over when you lose. It's over when you quit.