'study' vs. ' learn'

[Liza]

Hi again,

Could you tell me which is good?

1. She studies to play the piano.
2. She studies how to play the piano.
3. She learns to play the piano.
4. She learns how to play the piano.

Thanks a lot.
Liza

[Mister Micawber]

.
These are OK:

3. She is learning to play the piano.
4. She is learning how to play the piano.
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber