Beware that some of them are not legit at all. They often are parts of volume licenses, which, theoretical, are linked to one company. Because of that they mostly are single use and cannot be used to activate office a second time.
Yes, because it was a decentralized messaging protocol, like ActivityPub. The problem in the end was not the 'OG' XMPP Users but the new Google Talk users and how Google treated the protocol. This, theoretically, could happen with 'the fediverse', too.
I managed to put my family on wireguard. I said 'install this and come to me when you are done', I finished the setup and told them 'the key icon must always be visible'. I don't know how, but it worked 🤷