One Question About Steam Regions

Yes, you can claim it.

Trade/Acquire rest of world (ROW) versions and they should work fine.

Yes you can if you receive it as a gift. But I'm not sure if you will be able to see the store page after that. You should be able to though.

it uses GFWL correct? Is GFWL available in Turkey? Could that be why?

You can activate the gift, but I think you can't see the store page, since I have Dirt 3 (not available in my region), and I can't see the store page of the game.

it's fine if you receive a gift via Steam Trade or buy at online store like amazon.com, gamersgate.com and greenmangaming.com. but you still can not browse store page in Steam Client program. but you can browse in internet browser like IE, FF, Chrome and etc.

http://store.steampowered.com/app/57400/?cc=us

this way only for browse. 'cc' is country code 'us' means United State.

more country codes are here

You should try and create GFWL account first, it might not let you if your country is not supported. If that is the case then create a new account with the country set to UK or something like that then you'll be able to play it.
Most of the problems with activating steam gifts stem from russian versions since they're much cheaper than the US/UK/EU ones. As far as I know the most popular region-restricted games (even in gift form) are fallout:NV and Skyrim. These won't work anywhere else in the world.

Get the drm free version ;)

Of course you can, for example look at my library I got BulletStorm and it's restricted on my country. so don't worry about it.