Starting with your cylinders around arbitrary minor axes, one thing that did jump out at me is that there are quite a few cases where your cylinders were drawn with side edges that run either parallel on the page, or diverge as they move farther away from the viewer (as opposed to converging). We can see this in cases like 1, 10, 11, 12, 20, 21, 30, 43, 46, 51, 55, 56, 61, 62, 65, 66, 67, 68, 70, 71, 72, 75, 79, 91, 132, and 144. This suggests that the intention was to keep those edges parallel on the page, which as noted in these reminders is incorrect, and should be avoided, taking care to further emphasize the convergence if you're ending up with situations like this accidentally.

This issue does seem to be concentrated towards the first half of this part of the challenge (where it was happening close to a third of the time), suggesting that you became more aware of it and avoided making those particular decisions into the second half - so I don't think revisions will be required for that part. That said, do take more care when you go through the instructions - given that this was mentioned in a section for "reminders", where we go to some lengths to make it stand out, it does suggest that you might need to reflect on how you're going about familiarizing yourself with the instructions.

Aside from that, your cylinders around arbitrary minor axes are well done. Your linework is fairly confident, leading to smooth lines and evenly shaped ellipses, and you're mindful of the alignment of each ellipse as you identify their minor axes, catching both more obvious discrepancies and those smaller ones - which is important, as it helps avoid plateauing in our development of this area of skill as we continue to practice the exercise.

One minor point I should mention - which is not a mistake in that I don't actually explain this in the instructions (this is a case where I find something can be "discovered" more intuitively by doing the work, which can help develop a stronger understanding, which can then be bolstered by explaining it further in my feedback) - is to keep in mind that the two shifts between the ellipses on either end of a cylinder, whether in overall scale or in degree, both serve to convey the same information. That is, how much foreshortening is being applied to the form, or in other words, how much of the cylinder's length can be measured directly on the page, and how much exists in the "unseen" dimension of depth.

Because they convey the same information, this means that they do need to operate in tandem - lest the what the degree shift tells us contradicts what the shift in scale does. Generally you've handled this well, but I wanted to explain it in more detail just in case, as I noticed that in 121 on this page, you have a more dramatic shift in scale, but virtually the same degree between the two ends. The farther end should be a fair bit wider to account for how the cylinder is oriented in space, which the shift in scale captures more accurately.

Continuing onto your cylinders in boxes, your work here has largely been done fairly well. This exercise is really all about helping develop students' understanding of how to construct boxes which feature two opposite faces which are proportionally square, regardless of how the form is oriented in space. We do this not by memorizing every possible configuration, but rather by continuing to develop your subconscious understanding of space through repetition, and through analysis (by way of the line extensions).

Where the box challenge's line extensions helped to develop a stronger sense of how to achieve more consistent convergences in our lines, here we add three more lines for each ellipse: the minor axis, and the two contact point lines. In checking how far off these are from converging towards the box's own vanishing points, we can see how far off we were from having the ellipse represent a circle in 3D space, and in turn how far off we were from having the plane that encloses it from representing a square.

Aside from one thing - you're not extending the minor axis lines far back enough, and are instead only identifying them more similarly to the first section of the challenge, which can make it harder for you to compare those convergences at a glance - you're applying these instructions correctly, and so you're arming yourself with a fair bit of useful information to gauge how to adjust your approach page by page. Do be sure to extend those minor axis lines all the way back when practicing this exercise in the future so you can absorb that useful information with as few hurdles as possible, and you should be good to go.

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