I know this comment is kinda old just have to get A's, first time you'll get the first boss, then go to the second dong (forgot the name now) and click play and turn the screen upside down, you unlocked the third song, get an A, then it will play another song that you already played to get to the boss, get an A in this one and you'll get the last song if so. If the games close just open it again, if you already did it, that's good, but if you don't and tried and is not working despite doing everything told to do, then well- Idk, I'm sorry

just wait for a while and it will crash

depending on the song, the crash is likely a part of the gameplay. if it occurs, just reopen the game

i think the crash is the part of the gameplay. you have to turn your device around when at the level where the picture is flipped around

you can turn on the Low Resolution Mode in settings

may I see the gameplay