Im guessing you mean Open A?
A violin is not a note. It is an instrument.
It could mean many things. F is also a letter place holder for a note on the violin. Ex: F can be 2 on D.
A cello can play in the range of a violin (much of it), if that's what you mean, but a violin's highest note is much higher than a cello's highest note.
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2 fingers on A
violin
The longer the string the lower the note it produces
I assume you mean a chord. You can do this by placing fingers on both strings that you want to play and playing the strings at the same time.
The note A-natural sounds different on a tuning fork, a violin, and a flute because of the relative amplitudes of harmonics.
the note becomes lower
Yes, it means "violin."