I played piano about 5 years ago. I got placed “level 9”(second level, below the “performance level”) in a Chinese music school (famous). Does this help with college admissions (or it should be things that you did during high school?)? Thank you, 
As I noted on another post, I would not include anything before HS. The only exception would be some absolutely amazing accomplishment the caliber of an Olympic medal. This does not qualify.
If you stopped it doesn’t matter. If you continued with piano at any level, even for pleasure, then it can matter.
Playing piano is a common activity for many students and stopping piano 5 years ago isn’t special or relevant to who you are now. Rather than help with admissions, adding ancient history into your application makes you seem like you are trying too hard and cheapens current activities.
Short answer: no.
What have you done lately?
There’s an “ancient history” part of the application?
I would say not to add that since you have not been up to date with piano.
No, you needed to finish high school doing that. If you had started early and done through high school finishing at a high level (even if that’s similar to your middle school level - similar situation as my kid actually, though he’s moved onto other music stuff), it would be impressive. I wouldn’t even include it