Your work here is really well done. You've demonstrated considerable patience and care in each mark made, each form constructed, and all the analysis and correction you did afterwards. It's clear that your comfort with the concepts covered here have developed, and that you're at a level of comfort with constructing these forms and rotating them freely that will serve you well in the lessons ahead.

Starting with the first section - the cylinders constructed around an arbitrary minor axis - you've done a great job of hunting down even the slightest deviations in your ellipses' true minor axis from the one you were constructing around. This can be especially difficult, given that you have a big glaring line there insisting that it is the minor axis. It's very easy to simply say, "oh it was close enough" but you very clearly identified even the slightest discrepancy.

There is one concept regarding these cylinders that I hope students will pick up on while going through this exercise - but if they don't quite show that they grasp it, I of course take this opportunity to explain it. It has to do with the relationship between the shifts between the near and far ends of the cylinder - specifically the shift in scale that we're familiar with in perspective, and the shift in the actual degree of those ellipses, and how those two shifts are tied together.

Looking at your work, I see a lot of signs that you appear to understand that these two shifts are linked together as manifestations of foreshortening, at least on an intuitive level, if not explicitly and consciously. This principle basically means that if we have the far end getting considerably smaller than the near end, then the degree of that far end should also be considerably wider than the near end, as both of these occur when we have dramatic foreshortening. This conversely means that we should never see a situation where the degree shift is dramatic, but the scale shift is not, or vice versa. Throughout your cylinders I don't see any prominent cases where this is inconsistent, though I suspect you may simply have picked up on this implicitly. It further suggests a very strong grasp of 3D space, so good on you for that.

Moving onto the cylinders in boxes, you've really knocked this one out of the park with just how thorough you were. It is entirely expected that students will struggle with getting all their various parallel lines and axes to converge consistently towards their shared vanishing points, but the main focus of this exercise is actually a little bit sneaky. While it helps immensely to get students accustomed to constructing cylinders in specific, predetermined orientations and configurations, the degree of success we have (and that we can identify through the line extensions) all comes down to whether or not the box itself has a pair of opposite faces that are proportionally square. This exercise forces you to get better and better at making those faces square to start with, as it implies that the ellipses inside them will be circles, and therefore those rules regarding minor axes and contact points will hold true.

I feel that you got an impression of this in how you shifted your colour-coding, since you mentioned that there were underlying problems that would lead to others, and changing how you went about that made certain mistakes clearer. Personally I still see considerable value in grouping all lines converging towards a vanishing point in the same colour (as it reminds us that they must all share a vanishing point), but if you felt this change helped you identify problems more readily then by all means, keep doing it.

You've done a great job with this challenge, so I'll go ahead and mark it as complete. Keep up the great work.