Can Apple view my deleted imessage data in IOS15?

CLARIFY:My icloud storage has ran out. I don't have icloud+ but messages were turned on for iCloud. Can they view my deleted imessage data (Text, effects, photos, videos, recordings, etc.)? And if so, how do I truly delete it? To clarify, I said a lot of things as a young adult to my friends that are embarrassing.