Starting with your cylinders around arbitrary minor axes, I noticed that early on you started out by drawing cylinders with side edges that were entirely parallel to one another - effectively forcing their vanishing point to infinity. I'm very glad that you didn't stick with this, as it's actually incorrect. Reason being, we do not actually control where our vanishing point goes - we control the orientation we desire for the given set of edges, which itself determines the positioning of the vanishing point. The VP would only actually go to infinity in this manner if the set of edges in question were to run perpendicularly to the viewer's angle of sight - basically if it's not slanting towards or away from the viewer at all through the depth of the scene. This only is achieved for a very specific, limited set of alignments, and given that we're rotating our cylinders in this challenge randomly throughout (as we did for the box challenge), it would be incorrect to force those vanishing points to infinity.

That aside, you've generally done pretty well here - drawing your side edges and ellipses both with smooth, confident strokes, although there is one thing that I didn't stress too much in the lesson material that I do want to explain. The reason I didn't stress it much there is because I find that many students pick up on this themselves, and such understanding gained on one's own can stick more strongly, compared to something that was merely explained.

It is essentially the relationship between the two manifestations of foreshortening - the shift in scale from one ellipse to the other (where due to the convergence of the side edges, the far end gets smaller), and the shift in degree from one end to the other. Because both of these represent the foreshortening applied to the form, which serves to help the viewer understand just how much of this form's length can be seen right there on the page, and how much exists in the "unseen" dimension of depth, both shifts (scale and degree) must work in tandem with one another. So for example, if we look at a case where the scale shift is especially dramatic, like number 147, the degree shift is actually quite minimal, making the result look off (even if the viewer isn't entirely sure why). In this case, that far end should be much wider in its degree, to match the dramatic scale shift with a dramatic shift in degree.

Continuing onto the cylinders in boxes, 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.

You've generally done a good job with this, except for one part - the minor axes. I noticed that in the first half of this part of the challenge (150-200 or so) you appeared to be checking the minor axes, but were doing so more in the fashion from the previous part, where you were identifying them but not extending them as far back as the other lines. This can make it harder to gauge their alignment in comparison to the others, making it easier to miss important information. Then for the latter half of this part of the challenge, it seems like you stopped marking your minor axes altogether - which would more notably undermine the exercise, as it leaves an opening for mistakes to accumulate without being detected.

I'm not going to assign revisions on that front, but rather leave you to address this issue yourself in your warmups going forwards. Just be sure not to neglect any aspects of the exercise in the future. I'll go ahead and mark this challenge as complete.

Oh- and I would appreciate it if you uploaded your drawings as image files, rather than PDFs. Google drive is already kind of a pain to work with, as it requires me to click through each page individually (imgur is preferred because it allows me to scroll through all of the pages at a large size, allowing me to jump back and forth more easily), though I understand that isn't an option for everyone. Making each individual page its own PDF increases the load time between files however, making the issue a lot worse.