Jumping right in with the cylinders around arbitrary minor axes, for the most part you're doing very well. Your linework is confident and consistent, and your ellipses are smooth and evenly shaped, showing that you're adhering to the principles of markmaking well, and that you haven't slipped off that wagon in all the lessons that have passed between Lesson 1 and now.

The one thing I did want to mention isn't actually a mistake for the simple reason that it's not something I stress in the lesson material. It has to do with the relationship between the ellipses on the two ends, and the two ways in which they "shift" to convey foreshortening. That is, the shift in scale (where the far end gets smaller overall compared to the closer end) and the shift in degree (where the far end gets proportionally wider). These both serve as visual cues to tell the viewer how much of the cylinder's three dimensional length can be measured right there on the page, and how much exists in the "unseen" dimension of depth.

Because they represent the same thing - the amount of foreshortening being applied based on the orientation of the form - that means they have to work in tandem. I don't specifically mention this in the lesson material simply because it's something that some students pick up on (even if only subconsciously) just by virtue of drawing so many freely rotated cylinders, and understanding picked up in that manner tends to stick a little better. So, instead of sharing that information ahead of time, I prefer to reinforce it after the fact with a bit of explanation where required.

In essence, when you're drawing a cylinder with a far end that is much smaller than the closer end, be sure to match that shift in scale with a similar shift in degree. There are actually plenty of examples where you're doing this correctly - for example, many of those on this page fall into this category and you're handling them well. 147 is an especially good example of this kind of situation, so I think it's fair to say that this is something you are indeed picking up on subconsciously. I did still want to shine some light on it and explain it more explicitly because there are plenty of cases preceding this (like 116 and 119 on this page) where it's not being applied as clearly, so I figured it would be helpful to lay out the logic here.

Aside from that, I noticed a few places where you applied your hatching to the wrong side (113, 96, 94, 86, 82, 79, 65, etc...) which is admittedly odd because it's very clear you understand which side is which, so I'm assuming that you perhaps didn't give yourself enough time in the moment to consider which side should receive the hatching. Might be a sign that you should give yourself a little more time to make those decisions.

Continuing onto the cylinders in boxes, your work here is phenomenal. It's clear that you took great care in following the instructions. 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.

In applying those line extensions instructions as thoroughly as you have, you've armed yourself with as much information as you could about where your proportions were off, so you could meaningfully adjust your approach little by little to counteract those issues and refine your instinctual and subconscious grasp of those proportions and how what you draw on the flat page reflects upon the 3D structures being represented.

All in all, very well done. I'll go ahead and mark this challenge as complete.