Starting with your cylinders around arbitrary minor axes, for the most part you've done a great job. You've drawn these cylinders with a wide variety of orientations, your linework is smooth and confident (both for your lines which are smooth and straight, as well as your ellipses which are evenly shaped), and you've taken a good deal of care in fastidiously identifying the "true" minor axes for your ellipses throughout the set.

There is one thing I try to look for in this particular exercise that suggests whether or not a student properly grasps the various ways in which foreshortening manifests in a form, but it's a little tricky to find in your set. Reason being, you don't push foreshortening too far towards the dramatic, and otherwise stick with a range closer to the shallow end of things. So instead of trying to explain a particular mistake or issue I see in your work, I'm going to address this in more general terms just so you don't miss out on something from which you may benefit.

So the issue comes down to this - foreshortening itself helps to convey to the viewer an element of 3D space which cannot be directly depicted on a flat piece of paper. That is, just how much of a form's length exists in the "unseen" dimension of depth. If a cylinder runs perfectly perpendicular to our angle of view, then the length we see on the page is basically all there is of the cylinder. If however that cylinder slants towards or away from the viewer, and in any way comes towards us or extends away from us, then we need to be able to understand how much of its length passing through the third dimension.

This foreshortening manifests in the way these forms are drawn in two ways: a shift in scale, where the end closer to the viewer is going to be larger on the page, and the end farther away will be smaller, and a shift in proportional width, or in the case of cylinders, degree - where the far end is going to be wider than the end closer to the viewer. Now, you obviously understand both of these, because I can see you employing scale shift and degree shift throughout the set.

What some students miss however is that both of these shifts need to occur in tandem - roughly speaking, if the scale shift tells the viewer that there is lots of foreshortening being applied, we cannot in turn have the degree shift tell the viewer that there is very little foreshortening being applied. So if that scale shift is more dramatic, the degree shift should also be more dramatic, and vice versa.

Again - I don't really see any obvious cases where you visibly deviate from keeping them in line with one another (there are a few that I'm unsure of), but without seeing some especially dramatic foreshortening it's hard to tell for sure. So, I figured explaining it anyway would be best, even if this is something you already understand through having drawn so many cylinders.

Moving onto the cylinders in boxes, you've knocked this one out of the park. 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.

I can see that you've gotten especially adept with controlling how your lines converge, and that you've continued to develop a good sense of what proportions will achieve the desired results. Furthermore, you've been incredibly patient and careful in applying the line extensions, and have certainly benefitted from them throughout the set.

So, to that, all I can say is that you've done a great job, and that the instincts and spatial awareness you've developed here will certainly help you a fair bit into the next lesson. Keep up the fantastic work, and consider this challenge complete.