Won a game. Its region restricted

Do not mark it as received or you will eventually be suspended for not activating a win. You could tell him it is region locked, and if it's a gift, return it to him.

Can be a mistake. These days not all know what is region restricted or what not. I suggest you request him to send a RoW copy if possible and if not return it so he can request a new winner and can specify. Under any case return the gift if it is a gift or unmark Recieved option if you have marked it.

The maker of the giveaway has 1 week to deliver the correct game. Until then don't activate it, don't gift it away - return the game to him/her and if you get a working copy, mark it received, if you won't, mark it not received at the end of the 1 week

Pack up your shit and move to that region.

Just sent him the game back... Lets see how it goes. He now went offline -.-"

kinda sucks. but mistakes can happen, let's wait

6 ppl wants you to get suspended heh.

Giveaways are like donations. Gifts from Steam inventory are indicated with "region restrictions" but keys bought from online retail site may only indicate during the checkout.
Steamgifts are accessed by everyone and cross-purchase on online retailer is common. Certain games with region restrictions will be sold as region restriction according to their IP address.
There is no money or currency lose on your side. The gifter should not be held responsible as it's sort of a good will. It's just unfair for the gifter.
Just contact the user to re-gift to another winner, recreate giftaway with region restriction or you may just create a giftaway yourself with region restriction.

I had gift of Guild Collection, won on Steam Auction, it had any tags, but was region restricted, but I even didn't knew it was, no ANY marks

That was a steam gift, which clearly says: Restricted Region (Russian Countries or something)

What I like about questions like this is you always have a couple of barely worded wrong answers, and then a more detailed correct, rather specific, correct answer. Like you knew the answer before asking =P

more then likely a mistake, i didnt even know steam gifts could be region restricted