ask maybe,..

You can give it on the forum if it's for uPlay.Maybe use VPN if uPlay doesn't mind it?
PS:How do you activate uPlay codes?

The Steam version of AC3 uses Uplay as well, so if it looks like a Steam key, it probably is? However, you can't run a giveaway for anything that isn't redeemable on Steam.

You can bypass region restrictions with a VPN or proxy, but I won't delve into how due to it being against the TOS depending on platform.

You can't create a giveaway for it.

You shouldn't have an objection to Uplay though, since even the Steam version requires you to use Uplay. I'm not entirely sure if that code you received is different from the one a friend gave me (i.e. the most awesome-est friend ever) but I had to purchase the game through ubisoft's store, and the promo code they gave me reduced the price of the game to $0.00. I'm not entirely sure if there are actual regional checks for this process, considering you never have to pay anything. It's definitely worth trying out.