How do i know it's a ROW gift if it's not written ??

I think that if it doesn't say anything about the region, then it's region free. I could be wrong though.

Games without TAG = no region restricted, so NO TAG = ROW

Honestly even no TAG can't mean its region free. I remember Colonial Marines preorder gifts from Russia had no tags but they just added them a day before release. So if its a preorder gift, you never know.

If the game is out and has no tags, its region free. You can also check if the game even has different ids for different regions in the store.

Check SubscriptionID, you'll need a webbrowser plugin.

Check how to use SteamDB here. Check the ID of the the game: Go to the shop and hover your mouse over the cart: you will see e.g.
javascript:addToCart(32988);
32988 is the ID of the game, check at SteamDB what 32988 is, as you can see it's Democracy 3, has no tag and no restrictions.

If it is RU/CIS, it will be written, otherwise assume it's RoW. Care should be taken with pre-orders though. They can change the restrictions before release.