Sorry, no clue how they identified multi accounts, but I would guess via a similar means that you are using via IP address. But that is a guess. As for bots, they were also looking at accounts that were constantly farming the game non-stop 24/7. Both methods would be a bit of a programming challenge, and then to admin it, youch!
Yep, I am amazed at how many people on discord ask questions that are covered in the FAQ on the game's site.
You've built a great game, that does a good service to the music community. And THAT is why Rising Star Rocks!