We need option for restricted gift here

Decline as an option is useless on steamgifts. On steam you could get games you don't want. Here on steamgifts you ONLY enter for giveaways you want - so there is absolutely no reason for a decline option. Also you said 7 days is too long until you can mark it not received - well, that's the deadline senders have to deliver the won game. You can't force it to be shorter because you couldn't activate the first key you got. If it's a legit and honest user, he/she will need time to get a copy of the game without region lock.
Maybe I'm just thinking about this too kindly, but afterall - sending a duplicated, invalid, or region code or nothing at all - it's the very same at the end, because you don't get anything.
Don't be too harsh on a user who actually wanted to give away something for the community, but mistook the region lock/ wasn't paying attention to the rules. He's still much better than regifters, CV-cheaters or other people who just abuse Steagifts' system.

The case you receive a regional restricted copy is the same if someone sends you a desura or origin key instead of a steam key-> not received

A option to mark this just as a "decline a gift cause it is restricted" and allow the creator to do a reroll would be be pointless with the actual terms of steamgifts. Also an option like this would also have an 7 days timer,to give the creator a chance to correct his failure. It would solve nothing.... So still the best solution is solution that allows regional settings, instead tinker with symptoms.

You could not enter such an giveaway, no timers, no problems....all are happy