Is it possible to renew the tags and registration on a car that isn't in your name or does the person who is named on all the paperwork have to do so?

The best way to perform all legal paperwork in someone elses name is to aquire an special power of attourney, listing all actions needed by the individual and who is allowed to do it in their name. Another way that's quick and easy but is sometimes a bit more difficult to accept is a notorized letter stating what needs to be done and whos going to do it.