I still don't understand about games not available in my region...

Correc, there might be cases where you can activate and play a game that was bought somewhere around your region that you couldn't buy yourself since it wouldn't be listed on the store for you,. Giveaway wise, you either have global keys or regional keys, regional keys like asia, aren't meant to be activated in the usa for instance, or vice versa. That's because of pricing difference in those areas vs value of money, etc. It would become a business if people could just go to russia and buy cheap keys and sell to countries with like 10x the price. It probably is regardless, but it's mostly controlled.

Also right now with the russia ukraine war, a lot of companies blocked contact to russia, meaning keys for that area aren't provided and so will not activate.