I think youre work was well done. A lot of the exercise prior to the boxes were very clean and confident. I especially want to praise your ellipses. Its common for people to not keep the degree in the table of ellipses exercise but you've showed that you have a good control on the degree of the ellipses. Good job.

Now onto your boxes. Some of the box's perspective were inconsistent. Remember in 3 point perspective when you tilt a box up there's a converging point at the top and there's no converging point below the box. If you tilted the box down there's a converging point at the bottom and there's no converging point above it.

This might help you with creating boxes in 3 point perspective.https://imgur.com/a/fZXN9r5

In the rotated boxes exercise your 3 point perspective boxes(boxes on the top-left, top-right, bottom-right, and bottom-left) had similar perspective. Lets take your boxes on the top left for example, the box on the very left needs to have its converging point on the right be closer than the box beside it since its being rotated to the left (if that makes sense). Please go over how rotating a box can change it's converging points again before proceeding to the 250 box challenge.

Other than that I think you're well on your way to the 250 boxes challenge. That's where you'll start really understanding how a box behaves in 3 point perspective and should be able help you tidy up your boxes a bit more. Again, please go over how converging points change when you rotate a box before you go to the 250 box challenge. Keep at it, and always do your best!