How often are the 6th, 7th, and 8th needed on the violin, and can violin music live without these positions?.

Really anything can be played in different keys. But it's nice to know your way around the violin either way ^^ I played guitar before violin, i found it was hard to memorize 22 notes on 6 strings. But after time it all falls together.

I agree, one must know their way around their instrument. Thanks for your reply.

It really depends on the level/type of music you will be playing