You mentioned the order was wrong, but from what I can see... I don't suspect it is? I mean, you didn't number the first section (I can only assume you harbour some grudge against me - please number everything in the future :P ), but the second section is numbered and appears to be ordered correctly. Since I've nothing else to go off, I'll assume that the order is correct (aside from that one page of cylinders in boxes that got stuck early on).

Looking at your cylinders around arbitrary minor axes, to start you're doing a great job of executing your ellipses such that they're drawn confidently and evenly shaped. You're quite conscientious in checking your minor axes as well, identifying even small deviations to help you continue to grow and avoid plateauing from getting "close enough".

One thing I would have liked to have seen was more variation in terms of your cylinders' foreshortening. While there are a few that are oriented more towards the viewer, and as a result have a bit more of a dramatic shift in the scale of the ellipses as they move away from us, there's really only a few. Most of these appear to be roughly the same, just drawn in different rotations across the set.

One thing I purposely look for are areas where the two kinds of shifts from one ellipse to the other (one being the shift in degree where the far end is drawn wider than the closer end, and the other being the shift in scale where the far end comes out far smaller in scale than the closer end) don't maintain a consistent relationship. To put it simply, if the far end is much smaller in overall scale, it should also be much wider in degree. Never would it be roughly the same degree, but much smaller in scale. Unfortunately there wasn't enough of that kind of variation to base that judgment off, but from what is here, I didn't see that mistake.

I am however quite happy with the results of your cylinders in boxes. This exercise is specifically designed to improve students' ability to draw boxes that feature an opposite pair of faces which are square in proportion, in 3D space. We do this by taking the line extensions from the box challenge, which help us improve our ability to eyeball more consistent convergences towards a shared vanishing point, and add 3 lines from each ellipse: a minor axis, and the two lines created by the contact points. These lines will only align towards the box's own vanishing points when the ellipse itself represents a circle in 3D space that rests on the surface of the box. Therefore by checking for whether or not this is the case, and making adjustments to bring them more in line with the VPs, we gradually get better at estimating what kind of box will best suit this purpose, and improve our ability to instinctually create boxes with a pair of square faces.

To this end, I think you've done a great job, specifically because you've been very fastidious in checking your line extensions. While they're not perfect at the end, they do show a pretty consistent ability to get your proportions within a range that would read as being square to the naked eye. So, good work there.

While there are no more extensive challenges like this (just the 25 wheel challenge), the importance of numbering each instance is incredibly important. Not only does it clearly show me where you started and where you finished, it also allows me to identify if a student is trying to fake completion by showing the same pages (not that anyone actually does that), and perhaps most importantly helps me point out specific ones if I need to talk about them. Always number things like this.

So! I'll go ahead and mark this challenge as complete.