Never heard of this game. It sounds...interesting. The only rhythm games I've played are WarioWare and Geometry Dash, and those are arguably not rhythm games at all.
Lemon Demon is just the nickname of the monster, the monster's official name is Monster. And I also used to think that Philly was called Philly Nice, but the game says it's Philly so that's what's in the quiz.
You can make your own FMF quiz with all the mods you want (which I see you’ve already done, thanks to your link), but I want my quiz to not include any mods since that’s all unofficial FNF content. This quiz is only for songs from the base game.
Philly Nice is the actual name of Philly I think
Whether this is genuine or just to avoid copyright I don't know, but canonically it's Monster and not Lemon Demon.
Edit: it is 😔