My mechanic buddy used to mix three or four kinds together in a spray bottle. Gave it a name not repeatable in polite company. Not sure if acetone was in there but, to my knowledge, acetone and ATF was supposed to get farther in to stuck things than even PB. Maybe acetone and ATF were in there too. Yes, Acetone evaporates and seems to tend to eat plastics or make them more brittle if it is not mixed with something. Put with another liquid, I am not sure it does, or as fast.
PB has always worked better for me than Liquid Wrench. Yes, some people use Liquid Wrench. It seems to work well, sometimes, when PB, it has to be the most stuck bolt in the world - like, an exhaust bolt on a car that's 30 years old and seen nothing but heat - to really test PB and see what it can do. Even then, PB, by itself, sometimes works. Then you move up to the ATF and acetone mix.
If that doesn't do it, your best penetrating lube is a MAPP gas torch or an Acetylene torch.