I'm not going to ask you to go back and do an extra 6 wheels, but no, you really should not have deviated from the instructions. The course as a whole is pretty clear on that, going back to Lesson 0 - the tasks are assigned in a specific fashion, with certain goals in mind. Because students are not strictly expected to understand all of the reasons behind why an exercise is set out in a specific fashion, they just have to do what's instructed.

Anyway, starting with the structural aspect of your constructions here, you've largely handled them well. Across many of these you are including additional, slightly larger ellipses through the midsection to produce a sort of "bump" in their profile, which in turn gives them an inflated appearance - as though dropping it on the ground won't just "thunk" solidly, but rather it would produce a nice bounce, as a tire should.

That said, there are a number where a bit more of that kind of a bump would have been warranted. 14 and 9 for example do end up feeling a little stiff, and while this could be intentional (in which case that's fine), always be sure to make those choices consciously.

When it comes to the rims/spokes, you've been attentive to establishing both the outward faces of those structures, as well as the side planes which goes a long way to establishing them as solid, three dimensional forms.

Continuing onto textural component of the challenge, your work is somewhat more mixed. It falls into a couple categories:

Firstly, you've got the cases where you're definitely trying to work in filled areas of solid black, but you tend to use them more as form shading, rather than cast shadows. We tend to be prone to this when we draw what we see in our reference image directly, rather than understanding the nature of the textural forms present, and then inventing the cast shadows based on that understanding (as explained here).

That said, this issue - which we see most prominently in number 3 - isn't uncommon, and I have a bit of an explanation as to the difference that I wrote up for another student. Here's the diagram, and I'll paste the explanation below.

On the top, we've got the structural outlines for the given form - of course, since we want to work implicitly, we cannot use outlines. In the second row, we've got two options for conveying that textural form through the use of filled black shapes. On the left, they fill in the side planes, placing those shapes on the surface of the form itself, and actually filling in areas that are already enclosed and defined on the form and leaving its "top" face empty. This would be incorrect, more similar to form shading and not a cast shadow. On the right, we have an actual cast shadow - they look similar, but the key point to pay attention to is shown in the third row - it is the actual silhouette of the form itself which is implied. We've removed all of the internal edges of the form, and so while it looks kind of like the top face, but if you look more closely, it has certain subtle elements that are much more nuanced - instead of just using purely horizontal and vertical edges, we have some diagonals that come from the edges of the textural form that exist in the "depth" dimension of space (so if your horizontals were X and your verticals were Y, those diagonals come from that which exists in the Z dimension).

The other category would be where you tend to put down more arbitrary, little marks - like in 14 and 15. Here, it suggests that you're really just trying to sidestep the conscious, intentional thinking that is required to understand the nature of those textural forms. This kind of approach can be fine, depending on what you need, in general drawing, but for the purposes of what we're doing in this course, every mark we put down is the result of planning and forethought, and so relying on any kind of randomness is definitely a big no here.

Now, this textural aspect of the challenge is something of a trap. Students are usually so far removed from Lesson 2 at this point that many of them forget about the specific nature of how we talk about texture in this course, and so, like you, they're more likely to just wing it in whatever fashion.

Fortunately, falling into the trap is expected - so you won't be held back over it. Just be sure to review the texture section of Lesson 2. And of course, do not deviate from the instructions going forward. You only have one lesson left, so that's probably not going to be an issue, but... it might not be a bad idea review the Lesson 0 videos to make sure you're refreshed on how this course works.