We certainly understand that some people aren't able to use imgur, so it's fine as long as you've made the attempt to find something a little easier for us to work with.

Starting with your cylinders around arbitrary minor axes, your work here is by and large looking really solid. Your linework is excellent - no sign of hesitation, stiffness, wobbling, etc. and despite the highly confident execution of your marks, your ellipses remain very tight and consistent. You've also been quite fastidious in checking the alignment of your ellipses (catching a lot of small discrepancies which'll help you keep from plateauing early), and you're also demonstrating a strong underlying grasp of the relationships between the different manifestations of foreshortening - to be more specific, I mean how the shift in the degree of your ellipses occurs in tandem with the shift in scale. When one is shifted more dramatically, it's matched with a dramatic shift in the other, avoiding cases that would jump out as incorrect to the viewer where one such shift suggests a lot of foreshortening, and the other suggests very little.

Continuing onto your cylinders in boxes, you've similarly done a fantastic job. 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.

There's just one point that I wanted to call out, and that has to do with how you're handling the line extensions for the minor axes. I noticed a number of cases (like 159 and 157 on this page) which have the arrow heads on their tips pointing towards the viewer, rather than away. While this isn't that big of a problem (though just for the sake of consistency and ensuring that you're always thinking about lines in perspective as receding off into the distance, it's worth ensuring the arrow heads point in the other direction if you continue to add them), I did notice that this would often go hand in hand with the minor axis lines themselves not being extended as far back as the others. This can make it a little less easy to judge whether those convergences are correct/consistent, and to identify what adjustments you need to make. It doesn't make it so much more difficult, but there's no reason not to make it as easy as possible by avoiding discrepancies like this.

Anyway, I'll go ahead and mark this challenge as complete. Keep up the great work.