The game has triple checks with switch related to quest, previous answers and relationship. You are supposed to make exclusive quests resolved using cheats and then save the game. I am not sure if you can put previous answer (dialogue chosen in the past) with cheats.I mean that the save where all quests are completed and relationships are pumped.
Was simpler years ago: quests just increased the romance value and you could get the girls when maxed, they didn't care HOW you got them. Not they decided for a linear approach.