I prefer a satin finish, I find it’s less sticky. but it becomes glossy with years of wear so …
b) you can do it with fine (000) steel wool. I’ve done this a ton of times, including on Greenie and Juliette (my yellow Telecaster) to bring back the satin feel when it becomes glossy
and
c) no it’s not irreversible, you just have to polish the finish with a cloth and polish compound (paste), and it will become glossy