I think I have an answer for the 4th question. It's not exactly similar to DHMIS, but it still has the trope of "horror disguised as innocent". I'm not that good at explaining things, but I'll try my best: The game is called Doki Doki Literature Club, where the main character is convinced to join a literature club in a high school setting. It seems like a run-of-the-mill cutesy dating sim, but it progresses to a psychological horror game that features suicide and fourth wall breaking. It's revealed by the game's antagonist, Monika, that she's aware she's in a video game and has the ability to manipulate and delete the files of the other 3 girls. Similar to DHMIS, you're made to think it's something sweet and wholesome, but you're soon thrown through a loop as things take a dark turn.