I would like to donate a game to twitch streamer. But I do not know if his twitch email is used on his GOG account and I want it to be a surprise :P. So can he recieve even if his email is does not exist on GOG? And I have read that GOG do not have regional restrictions but some exceptions. Is from Brazil to Canada one?

The gift is not bound to the email address you send it to. Send it to yourself, then send the code you receive to the actual recipient in whichever way you wish - carrier pigeon, hand-written letter with a rebus, record an audio file and send that via Facebook... the possibilities are endless.

Be aware, though, that you will most likely pay the US price (that's the "base" price) for the gift, not the Brazilian (regional) one.