Starting with your cylinders around arbitrary minor axes, overall you're doing pretty well - your linework is confident and well executed, your ellipses are smooth and evenly shaped, and you've included a great deal of variation in your rates of foreshortening. I'm also pleased to see that you're checking your minor axes quite fastidiously, catching fairly minor and easily missed errors - the sort of thing that will help you avoid plateauing in your skill development as you continue practicing this exercise going forward.

There is one thing I wanted to mention, although this isn't 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 your work, I am seeing the beginnings of that understanding forming (for example if we look at this page, 148 shows a more dramatic shift due to how it's facing the viewer more, whereas 147 has a minimal shift due to it being oriented more perpendicularly to the viewer), but I did feel it might help solidify the understanding that is developing if I explained it more explicitly. In essence, if you have a more dramatic shift in scale, always be sure to match it with a commensurate widening of the degree - otherwise the viewer will pick up on something being off, even if they don't know exactly what it is. Of course you don't need to worry about being exact - just a general push to increase the degree, the more you shrink the far end, will serve you just fine.

Continuing onto your cylinders in boxes, your work here is generally well done, although I have one suggestion on how to adjust your approach to increase the effectiveness of the exercise - I'll get into that in a moment. First, some context.

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're applying the line extensions well, although you're falling a little short in one area - the line extensions for the ellipses themselves (the minor axis lines as well as the contact point lines) are quite literally too short. Ideally we'd want to extend them as far back as the boxes' lines, so we can compare the convergences of each set of lines as easily as possible at a glance. Leaving the ellipses' lines shorter adds to the mental steps we have to take to glean useful information from them, and that's an additional hurdle that simply isn't necessary.

Aside from that, your work is looking solid. I'll go ahead and mark this challenge as complete.