Q: Can one ever use the out-of-turn function of a Surprise during one’s own turn?

A: If you use the Surprise card as one of your plays during your turn, then you must use the “during your turn” functions. The “out of turn” functions almost always cancel some other card play, and it is not allowed to cancel your own play with your own Surprise. Thematically, consider this: it’s hard to really call it a “surprise” if you’re doing it to yourself in this manner.

The only time when you might not use the “during your turn” on your turn is when you’re using a Surprise to counter a Surprise played by another player against you during your turn.

See Does countering a Surprise on my turn count as…