It's common. Though, in the case of the ellipse you mentioned, the issue is not so much with it, as with the axis line (not being equidistant from the arcing lines). In which case, we wouldn't fault you for the ellipse not folding properly. Still, all we look for is that the student is trying to follow the instructions - we don't expect them to nail it every time, nor do they, so I wouldn't worry.

Unfortunately, no. I'll recommend splitting those boxes equally between the 14 days, so that you give your chance the best chance of improving as much as possible (as opposed to doing them all in one day), and spend the rest of your time drawing for fun.