1. What are skew vectors?

Skew vectors are three dimensional vectors that never meet.

2. Can the length of a three dimensional vector be found?

Yes, just like the magnitude (length) of a two dimensional vector can be found using Pythagoras' Theorem √(x2 + y2 )

there is a similar formula for three dimensional vectors, √(x2 + y2 + z2) also derived from Pythagoras' Theorem.