Giveaway game which i won on this site

Yes it is. As long as you activate the won game in your account there is no problem.

Yup, its perfectly fine if you won a game and then later it happened to be in a bundle that you want to buy

Yes.

Yes. As long as you activated your previous win for that game. If you didn't then it will look like you are re-gifting.

If you redeemed the key / gift you won here on your Steam Account, than there is no problem with giving away the same game :)

You have to activate the games you win here, so as long as the one you are going to giveaway is not the actual game you won here you can giveaway any game.

I have won games here, activated them and then later bought a bunch of the same games and gave them away.

Thanks :)