Congrats on finishing the cylinder challenge! I'll do my best to give you advice so that you can improve.

Starting with your cylinders around arbitrary minor axes, you've done a great job. Not only are you consistently executing straight lines that are smooth and consistent, and ellipses that are evenly shaped (suggesting solid use of the ghosting method), you're also checking your alignments fastidiously, identifying even small deviations - the sort of thing that can cause a student to plateau as they get into the "close enough" territory, if missed.

One thing to note however, some of your cylinders ended up parallel (99, 77, 33) which isn't a huge problem as it's only present in a handful of them but it's still best to explain why that isn't possible. The thing is, we do not actually control where the vanishing points should be. Rather, we control how our edges in 3D space are oriented, and it is that which controls the location of the vanishing points. Specifically, a vanishing point would only go to infinity if the edges it governs run perpendicular to the angle at which the viewer looks out into the world - basically, where those edges do not slant towards or away from them through the depth of the scene. Since we're rotating our cylinders randomly throughout this challenge, the chances that they'd align so perfectly is small enough to be avoided altogether - so in the future, if you aren't fully intentionally aligning a set of edges that specifically, be sure to include some visible convergence, even if it's only very slight.

Moving on to your cylinders in boxes, unfortunately there is a major error in the way you've applied the error checking method. If you take a look at this https://drawabox.com/lesson/250cylinders/1/stage2check you will see that there are 6/7 lines that extend from each side of the box. If some of the line extensions are neglected, it undermines the purpose of the entire error analysis, and thus the exercise as a whole. 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.

If however you neglect, one, two, or half of the lines that we're extending, then you leave places for those errors to hide and go unnoticed. Thus, the growth and improvement we seek to gain in the assigned work, specifically in honing our estimation of those proportions, is limited at best.

Unfortunately, for whatever reason - and that may be something for you to reflect upon and identify - you did not follow the instructions here as closely and as carefully as you should have. I would guess that given the repetitive nature of the challenge, you may not have gone back to review the instructions, to make sure you were applying everything correctly, and may have gone into auto-pilot as a result of the monotony. Even I've done it while I was doing the challenge.

In addition to this, there are two things that we must give each of our drawings throughout this course in order to get the most out of them. Those two things are space and time. Right now it appears that you are thinking ahead to how many drawings you'd like to fit on a given page (apart from the last 2 pages). It certainly is admirable, as you clearly want to get more practice in, but in artificially limiting how much space you give a given drawing, you're limiting your brain's capacity for spatial reasoning, while also making it harder to engage your whole arm while drawing. The best approach to use here is to ensure that the first drawing on a given page is given as much room as it requires. Only when that drawing is done should we assess whether there is enough room for another. If there is, we should certainly add it, and reassess once again. If there isn't, it's perfectly okay to have just one drawing on a given page as long as it is making full use of the space available to it.

Finally as with the cylinders around a random axis, you have some boxes that have sides that are either isometric (not converging) or diverging (207, 225, 247) similarly to the cylinders they aren't that common but always remember that lines parallel lines are always converging towards a vanishing point

Therefore, I'll be assigning a revision of 50 cylinders in boxes. With these 50 make sure you properly check the ellipses inside the box in addition to the minor axis + sides of the cylinder which you've done. If you have any questions or need clarification on anything don't hesitate to ask!