I think they are at least partially compatible, but how much so? Can generation 1 and generation 2 cylinders easily and effectively be combined in one pneumatic pipe system? I.e. a set of pipes, tubes and other parts that exchange the air and are pressurized by the same pump. And how can possible problems be overcome?
https://www.wikiwand.com/en/Lego_pneumatics describes the various generations.
They describe V2 more as generation 2.1, pistons changed, but tubing and t-pieces stayed identical. Therefore I think it's safe to say that it's entirely compatible with all pneumatics from 1985 on ... The pneumatics prior to that is a different story...
I didn't know about gen 2.1, so I've updated my question to make it clearer. Can gen 2 pumps be used to create underpressure for the gen 1 pistons? Aug 24, 2022 at 19:04
That was not necessary, it's merely the nomenclature the article uses, lego uses V2 Aug 25, 2022 at 6:16