north vs south

He can't change game, but you can allow him delete giveaway to prevent him get red unrecieved mark, which would be fair as you recieved game, but wrong version.

No, creator can't do anything to change it nor staff, you either let the gifter delete the giveaway and you agree, or you ask he will give you a proper copy, or he deals with the not received, eitherway mark it as not received.

GA creator will have to create ticket for changing giveaway game. However, junior mods can't change it. so both of you will have to wait longer than usual.

Sometimes a publisher loses the rights, delete it from steam and then get them back and put them back on steam with a new subid or it gets replaced with an updated version of the game.
So you can have a game twice but still have a different subid, so they can be the same game. In this case i can't say if it's an upgraded version, i think it's the exact same one. But still you should mark it as not received as for sgtools.info it would say you didn't redeem it.

Contact the gifter, a correct copy is very cheap for him to get (not that he is forced to) or have the giveaway deleted, either way mark it as not received, that's the only thing left you can do.