Present perfect with "from"

It should probably be rearranged to "I have been learning to play" since learning is a continuous action. This is probably the best if you are still playing/learning, but if you have ceased the action "I learned to play" is probably best, in all settings.

Informally any of these variations will transfer adequate meaning.

I would use the present perfect continuous if you started learning to play the guitar in the past and are still learning: "I have been learning to play the guitar from an early age."

If you learnt how to play the guitar at an early age, which is now in the past, use past simple.

as of a date, as from a date

But: at any early age is more idiomatic here.

• I started learning to play guitar at an early age.
  OR
• I started learning how to play guitar at an early age.
• I've been learning how to play guitar as of or as from my 10th birthday.
• I've been learning how to play guitar from an early age.
• I learned to play [or how to play guitar] when I was very young.
• I've been playing guitar since I was young.
• I have learned guitar and now I'm learning the piano.

I would not use: have learned for the playing guitar thing as it is not very "actively oriented".

• I learned English as a child.
• I have learned how to write in French with much effort.
• I have learned French and now I'm learning Chinese.