I beat the game on accident(dont ask) and i still didnt unlock any stages!!!!!!!!!!!!! Please help!

You beat The Last? Please use the correct terminology.

Not completely. I got the first two VIPs on everthing and all three VIPs on the first few, I have all songs(including ~eteral love mix~), modes, and dancers (including pizzabox, and I dont even have that planet!), and everthing else, but there has never been a new stage in the shop!

You need to get the VIP cards for Pizza Box.

Get EVERY VIP card. That should have been obvious.

Ok, that happened to me too ... I understand that I didn't actually beat the game, but how did I suddenly get all songs (including boss songs), courses, arrows, modes, and characters available in the shop for no apparent reason?

(And of course I also didn't get any stages)

The reason everything suddenly became available to you in the shop was that your total play time for the game reached a certain level. It's an alternate unlock method Konami added for beginner players so they don't get too bored with the same songs. I've been looking online to see how long you need to play in order to unlock everything, but I can't find it anywhere. Could you give me an estimate as to how many hours you had logged on the game when you posted this question? Thanks.