Question

No... you have to activate your splice that you won though.

No, but its a scummy move if you already own the damn game...

No, unless you give away the key you won instead of other keys.

I dont think but it would be better you give this game directly or something different from creating giveaway its only a bundle game and not effect your contribution value...

Well, you're not allowed to enter for games that you already own, so yes, you could get banned.
But it depends on which came first. If you won first, then there's no problem, but if you bought the bundle first, and activated it, then won, you are violating the rules of Steamgifts