Apparently, the game is going through the final stage of testing (this is how the last enemy, Golden Frederica, comes out).
After version 1.0, the author will make the second part and supplement the first with new scenes (female domination and ordinary scenes).
Finally, the game will be completed.
And yes, except for one scene, there are no new sex scenes in version 0.99.
Just challenges and nothing else.
So 0.20 is the most optimal version at the moment and it makes no sense to go for the pre-release version (since it is not much different from 0.20).