Re: master mechanic?
ASE won't allow you to take one of their tests with out at least 2 years experience.
That's no guarantee you will pass though.
The functions of the ASE testing is to test your experience, test your ability to understand what you're reading (crucial to being able to understand the service info for what you're working on), and also test your common sense.
Seen plenty of smart techs out there that aren't certified, and a couple of dumb-dumbs who squeaked by, by picking enough right answers. Most of them don't make master tech though, and certainly don't make L1 or L2 (advanced level specialist).
My manufacturer master tech status has long since expired, since I have long since not worked for that dealer. Prerequisite for that was ASE master, and attending about a dozen 2-3 day long classes, then maintaining that status by attending any new model training classes.