It's not tricky at all; the extra options for the first 2 scenes are related to how many lives you had left when you got defeated. The first option is for losing your first life (which counts as the girl losing her virginity), the second is losing your second life, and the third is for losing your last life. The first 2 variations play out almost the same except for some extra dialogue about the girl's virginity, while the 3rd is extended and has her getting fucked so hard she can't fight anymore. The 3rd scene is what you get after a game over, so there's no variations (at least not in the demo).
There should be a scene for losing a life to every type of enemy, but they're locked out of the demo.