Looking at the picture below, what are two things that you would correct about this students posture and playing position if you were the teacher

The linear perspective changed the quality of art because it gave art a sense of reality. it gave the illusion that the background and surroundings were actually close and/or far and a sense of depth. linear perspective change the quality of art following its birth the renaissance period as they want the art to be more realistic and they believe one way to achieve it is to use the method of linear perspective. it uses the principle of math to realistically portray space and depth in art. 

Yes and no because if you know the vocabulary used you will understand it and go faster but you might not need it