Question

Well, I guess, Puzzle Agent is better :P

No and tell the creator to contact support.

You should not have accepted Puzzle Agent and asked for the game he originally gave away. You should say you did not receive it, but first reason with him some more...

Tell the person that you received the wrong game, and see if he/she plans on remedying it. If not, then mark as not received.

Check no.

No.

Don't check yes because the proper game isn't activated on your steam account. You have to wait 7 days before you check no. Try contacting the person to let them know you got the wrong game. They may have the key for the right game and fix the mistake (although you'll have to keep Puzzle Agent because you activated it). Once you check no, you can always change it back to yes if you end up getting the right game from the guy.