First off, congrats on finishing the 250 Box Challenge!

Starting with your lines, they have remained generally confident all throughout and I can see your convergences getting better over time. You started out having difficulties such as extending your lines in the wrong direction as well as hatching the wrong box face, but this also drastically improved as your drew more boxes until you were no longer making this mistake by your 8th page, so good work on that.

With your first couple of boxes, I can also see you were struggling with your lines ending up diverging or being parallel rather than converging but along the way this also started improving as well. With regards to your boxes' foreshortening/rate of convergence however, there wasn't a lot of variation, so that's something you could work on more. You're also still having a problem with your inner corners from time to time. There are still instances where they are diverging away rather than converging. If you take a look at this diagram, you can see that the inner corner is more or less parallel with the other center line of the box. A tip I could give is ghosting the inner line first to see whether or not its parallel with the center line already drawn. Thinking of that inner corner in relation to the center line will help to improve your convergences.

Overall there was a really big improvement from your first page all the way to your very last page and I can see you essentially got the gist of the lesson so I'll go on and mark this lesson as complete.