Starting with your cylinders around arbitrary minor axes, you've done a pretty good job! I can see that you've varied your rates of foreshortening a fair bit, you've been quite fastidious and careful in checking the true alignment of your ellipses, and for the most part you appear to understand how the two distinct manifestations of foreshortening are meant to work in tandem.

That is to say - foreshortening manifests through both the shift in scale, where the end closer to the viewer is larger and the end farther away is smaller, as well as a shift in degree where the far end gets wider than the end closer to the viewer. While most students do understand and apply this, I have to watch out for situations where students apply them inconsistently. Since they both represent the foreshortening applied to the form, if one of these shifts is more dramatic, then so too should the other be dramatic as well. Looking at your work, it seems that you have understood this - either consciously or subconsciously. In the case of the latter, I find that explaining the mechanics anyway helps solidify that understanding further.

Continuing onto your cylinders in boxes, these are done okay, but there is one key missing point that is causing you some trouble. The main focus of this exercise is to train students' instinctual grasp of how to construct boxes that feature two opposite faces which are proportionally square. We achieve this similarly to how the box challenge builds up one's ability to construct boxes with three distinct sets of parallel lines.

By adding the ellipses and their own lines (minor axis, contact point lines) to the line extensions, we're able to test how close the ellipses are to representing circles in 3D space. The closer their lines are to converging towards the box's own vanishing points, the closer the ellipses are to representing circles. And in turn, the closer the plane enclosing each ellipse is to representing a proper square in 3D space.

There are two ways in which you're kind of undermining this - though not so much that you haven't clearly made progress throughout the set. Firstly, I don't think you're extending your ellipses' minor axes, instead focusing only on the contact point lines. This means you're only testing some of the criteria, and missing an important piece.

The other case is that in a number of instances, you draw your ellipses such that they don't touch all 4 edges of the plane they exist within. I understand why you're doing this, to try to make those ellipses match the circle criteria even when the plane itself won't allow it - but when doing this exercise in the future, it is more effective to simply draw ellipses such that they touch all four edges, and then use the ellipse as part of an analysis. Let the extensions show you where you were off, so you can adjust your approach for the next page of boxes.

All in all you are doing good work, but have a couple things to keep in mind in regards to that last exercise. You're still good to consider this challenge complete - but with all exercises, be sure to continue practicing them as you move forwards, as part of your warmups.