Jumping right in with your cylinders around arbitrary minor axes, while there's a lot you're doing well here - your linework is very confident, you're quite fastidious in checking your ellipses' minor axis alignments, you're varying your rates of foreshortening a great deal, and so forth - when it comes to the shift in degree from one ellipse to the other, it's a bit more of a mixed bag.

That is to say, I noticed a lot of cases - like 60, 61, 64, 66, 68, 76, 81, 84, 107, 112, 127, 131, and so forth (there are others, I just scrolled through and wrote down a bunch of those I saw) where the degree of your ellipses were largely the same from one end to the other. There were also some, such as 74, 106, and 116 where the farther ellipse appeared to be wider than the end closer to the viewer, when it should have been more significantly narrower instead. Now, there are a ton of cases here where your degree shift is entirely fine and correct, but this does suggest that you may not be paying as much attention to considering what degree to draw that farther end, and that it will need more attention from you going forward.

One point you can keep in mind is that the more dramatically the scale shifts from one end to the other (where the ellipse closer to the viewer is larger overall, and the ellipse farther away is smaller), your degree shift is going to be more dramatic to match, as both "shifts" signify the same thing. They tell the viewer just how much foreshortening is being applied, and therefore just how much of the length of the cylinder exists in the "unseen" dimension of depth, and how much of it can be measured directly on the page.

Continuing onto your cylinders in boxes, overall you're doing 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.

By and large you've made good use of these line extensions, although the one area where I your work may stand to benefit the most is by working on your ability to draw ellipses inside of those planes (the ellipses in planes exercise from Lesson 1 being a good one for this, as one might expect, so it might be a good idea to ensure that one has been in your warmup exercise rotation). Reason being, the ellipses are meant to "describe" the plane containing them, so that the line extensions we derive from the ellipses continue to be relevant to that plane. By and large you've still done this pretty well, but I could see that some ellipses were looser than others, and this can throw off just how useful those additional line extensions can ultimately be - so the better you can get at freehanding the ellipses such that they continue to be confident and evenly shaped, but fit better into the plane enclosing them, the more you'll get out of the line extensions that follow. So ultimately, keep working on keeping your ellipses tight/consistent, but also on getting them to touch all 4 edges of the plane enclosing them.

Anyway, all in all good work, so I'll go ahead and mark this challenge as complete.