Starting with your cylinders around arbitrary minor axes, your ellipses are definitely drawn quite well, and are showing a good deal of both control and confidence. One issue that does stand out however is that while you definitely press into greater foreshortening later on in the set, earlier on (and in various instances later on as well) you appear to have a ton of cylinders where you're trying to keep the side edges of your cylinders parallel, and effectively maintaining the same overall scale of the ellipses on either end, varying only their degree.

So the problem is this - foreshortening (which is both manifested in the shift in scale where the far end is overall smaller than the closer end, and in the shift in degree where the far end is wider than the closer end) tells viewers roughly the amount of distance between those ends, and allows them to judge the length of the form. This means that the amount of these shifts should be fairly equivalent - a little scale shift should be paired with a little degree shift, and a lot of scale shift should be paired with a lot of degree shift. If they're different, that's an inconsistency the viewer's going to be able to pick up on.

It also means that if there's no foreshortening (like in your cylinders with no change in scale), then it's telling the viewer that the cylinder has a length of 0, which is obviously incorrect. So, always incorporate at least a little foreshortening, unless (as discussed in Lesson 1), your cylinder is specifically aligned to the viewer's angle of sight, resulting in a vanishing point 'at infinity'.

Moving onto your cylinders in boxes, you definitely handled those basic principles of perspective better here, so you're generally aiming for concrete vanishing points more consistently. Your work throughout this section is coming along pretty well. There are some ellipses that get a bit stiff and uneven (like 244) but most of them are still confident and smooth, and you're doing an excellent job of applying the line extensions. This as a whole has definitely helped you improve your ability to estimate the proportions of your boxes beforehand, to aim for a square plane on opposite sides, in which to place your ellipses. That's effectively the focus of the exercise - to build up your ability to estimate squared proportions in 3D space. By checking the ellipses' lines, we can see if they align to the box's own vanishing points. If they do, the ellipse represents a circle in 3D space that rests upon the surface of the given box, and therefore the plane that encloses it must be square.

So, I'll go ahead and mark this challenge as complete.