Oh good God, no, no, no... Sorry, gonna have to step in and stop the misinf. (EDIT: though I figure, technically, not REALLY misinformation lol)
Each "version-up" gives exactly one new Scene, say, v1.80 gave Scene 15, v1.81 gave Scene 16 (maybe the one prior too, sometimes; not sure about that, though). That's just how the dev works and releases. HOWEVER, they always have ALL the previous content as well, just, you know locked away. Guess they are a little greedy (would have you buy in a good number of times for all the scenes this way); but most people are, a little bit, no?
Incidentally, that's why the IF size went from ~250MB to ~450MB between v1.00 and 1.81. With v1.81 they had a nice and even 16 scenes (1.00, 1.01, 1.10, 1.11 ..., 1.80, 1.81; also, iirc there's like two scenes that make up "one" situation most of the time, like Scene 1="introduction *cough*" - Scene 2="conclusion...broken *cough*", rinse and repeat).
Same logic applies to v2.xx. They just started anew.
So all you need is a(n unlocked) v1.81 and a latest v2.xx (unlocked). Definitely NO "putting on top" and whatnot.
Just saying.