Starting with your cylinders around arbitrary minor axes, there's an issue that is present all the way through the first 100 or so cylinders. After about 111, you start shifting away from this issue, but the fact that it is present throughout so many of these is a problem.

The issue is that you have drawn those cylinders without any foreshortening at all. The side edges remain parallel on the page itself, rather than converging towards their shared vanishing point. The only situation in which lines that are parallel in 3D space would also run parallel with one another when drawn on a flat page, is when that set of lines specifically runs perpendicular to the viewer's angle of sight - so basically running straight across their field of view without slanting towards or away from them.

Given that this exercise has us drawing forms that are rotated freely in 3D space, we can basically assume that this perfect of an alignment would never occur. Furthermore, I did specifically ask in the instructions as shown here for students to include a wide variety of rates of foreshortening.

In the remaining cylinders, you have included one of the major manifestations of foreshortening - that is, the shift in scale from one end to the other where the converging side edges cause the far end to get smaller than the end closer to the viewer, but you are missing the other sign of foreshortening. That other shift is occurs in the degree/width of the ellipses, making the far end get much wider than the end closer to the viewer. If we look at more dramatic cases, like cylinder 130, I'm not seeing any of this shift in degree - this is where the shift would be most noticeable, because the shift in scale and the shift in degree occur together. If one is more extreme, the other should be more extreme as well.

You can learn more about this shift in degree in the Lesson 1 ellipses video.

Moving onto the cylinders in boxes, these are definitely better. The exercise itself is about developing a students' capacity to construct boxes which feature two opposite faces which are proportionally square. We do this by taking the line extensions from the box challenge and adding to it three new lines for each ellipse - the minor axis and the two contact point lines. For the most part, you've done this quite well.

By checking whether the ellipses' lines converge towards the box's own vanishing points, we can see how far off we are from the ellipses representing circles in 3D space, and therefore how far the planes that enclose them are from representing squares. I feel you've developed on this front quite well, though you had a few cases where the boxes were pretty wacky (not sure what's going on with 216 for example).

One thing to keep an eye on though is with the cases with longer boxes - when you allow there to be a fair bit of distance between the two ends of the box, you have a greater tendency to have their lines converge off in pairs rather than having the box's sets of 4 lines converge consistently (like 245, where the bottom plane's lines converged far more rapidly).

Anyway, you do need to resolve the issues with the first section of this challenge, but the second section is coming along well. I'll assign your revisions below.