I solved question 2 where v1 and v2 are unit vectors because their norms are equal to 1 AND they are orthogonal because the dot product v1*v2 is...

I solved question 2 where v1 and v2 are unit vectors because their norms are equal to 1 AND they are orthogonal because the dot product v1*v2 is equal to 0.

However, I'm not sure how to set up a system of linear equations for orthogonality in Q3?

Also, does Q4 imply there are more than one solutions for v3? In that case, does that mean v3 is not unique?