While Teslas are required to have a 12v due to federal regulation they do not to my knowledge require any checking or maintenance. They’re basically unused in the car, you can’t even get to them without removing stuff.
Tesla uses a lithium 12V now due to problems with the leas acid one they used previously. So they are definitely used, most of the electronics outside of the power train are 12V.
True for now. Next generation architecture seems to be moving to 48V. This is expected with the Cybertruck and all following architectures.
Ah hmm, I guess you're right. So just the alternator and starter are gone.