Which sentence is correct?

[arzgol]

He has played pianino from childhood since he was 6 years old.

He has played pianino since childhood when he was 6 years old.

Sometimes people say ''I prefer A over B'' but I'v learned ''I prefer A to B''.
Are both correct?
　
Thank you in advance.

 

[birdeen's call]

He has played pianino from childhood since he was 6 years old.

He has played pianino since childhood when he was 6 years old.

Sometimes people say ''I prefer A over B'' but I'v learned ''I prefer A to B''.
Are both correct?

Yes, they are. "To" is more frequent. Note that it should be (for example)

He has played the pianino since childhood. He started when he was 6 years old.

Also note that a pianino is a small piano. "Pianino" is a fairly uncommon word.

 

[arzgol]

Does it mean there is no difference between 2 sences. If I use since or when the meaning of my sentences won't be changed.

Thank you for spending your time answering my question.

 

[5jj]

Does it mean there is no difference between the 2 sentences. If I use since or when the meaning of my sentences won't be changed. .

That is not correct.

Both your original sentences are not natural English. Look at how BC used 'since ' and ' when: He has played the pianino since childhood. He started when he was 6 years old.

You could also simply say: He has played the pianino since he was 6 years old.

The age of 6 is clearly in his childhood, and if he has played 'since' then, it is clear that that was when he started.