Starting off with your cylinders around arbitrary minor axes, I think you're largely doing a pretty good job. Your corrections (identification of the true minor axis) are on point, and as you progress through the set your ability to get the alignment of your ellipses right definitely seems to improve. There is one issue I noticed, though:

You're pretty consistently focusing on cylinders with really shallow foreshortening. You're doing these reasonably well (aside from the odd time you draw the far end larger than the near end), but you're not getting much practice with cylinders that have more dramatic foreshortening.

Since you're not getting practice with more dramatic foreshortening, you ended up missing on something I hoped students would pick up on (or at least have the opportunity to pick up on) in regards to the relationship between the shift in scale between the near end and the far end (how the far ellipse is smaller in scale) and the shift in degree from one end to the other. Basically, both are aspects of foreshortening. The longer the cylinder is, the smaller the far end will get, and the wider it will get as well (relative to the near end). This means that you're not going to end up with situations where the far end is smaller but roughly the same degree, nor would you end up in situations where the far end is much wider, but roughly the same size. I saw a couple instances of this last scenario among your cylinders.

When practicing your cylinders in the future, make a point of practicing both dramatic and shallow foreshortening, and pay attention to this particular point.

Moving onto your cylinders in boxes, you are doing a relatively good job except for one important point - I think in a lot of these, you stopped identifying the minor axis of your ellipses correctly. In fact, I think in a lot of these, you tend to draw the minor axis where it should be, but not where it actually is.

The thing about this exercise is that it's actually more about the boxes than it is about the cylinders. Specifically, it teaches us to more intuitively draw boxes that have at least two opposite faces that are roughly square in proportion. Not exactly cubes, but parts of cubes, at least. It teaches us this by taking the concept of extending our lines to identify whether or not our lines converge consistently towards their shared vanishing points, and adds in a cylinder as an additional error-identifying tool. If the contact points and minor axes align properly with the other extended lines, then it suggests that the ellipses represent actual circles in 3D space - which in turn means that the plane that contains them must be a square in 3D space.

This of course relies heavily on actually identifying your minor axis correctly. I took an ellipse tool and actually identified the true minor axes of the ellipses on 3 of your cylinders here. As you can see, they are quite a ways off.

Now, all things considered, you're still doing a pretty decent job, but you may be getting a little lax and need to stay on your toes. I'm going to mark this challenge as complete, but be sure to keep practicing these as part of your warmups.