Question about Dark Souls 1

in your inventory, when you select the gift, says where he is locked

Yes, you will be able. If GFWL will still exist then, be sure to sign up on GFWL and put your country as Austria or something that supports GFWL. You will be able to play online and everything.

Source: I've done the same thing.

Yes, you will be able to activate and play it.

For what it's worth, Dark Souls appears as "Not Available" for my country too. I bought a key on amazon and it activated without problems

Yes. I had the same thing with operation flaspoint red river and dark souls. I activated both just fine.

I bought retail version from Altex ( ye I`m a romanian too) and I activated the key with no problem on steam, it says nothing about being unavailable or something yet...