Sounds like you did exactly what you needed to for this project. Learning to simplify complex subject down to simple structures is foundational for drawing. You will learn to see boxes, tubes, and spheres in everything. Your hand drawings are looking great. Particularly the one on the top of the second image. The perspective and proportion look solid. The hand with the foreshortened fingers on the first image is extra difficult, so I made this demo to help students. It may not be how Stan does it, but I find it really helpful to start loose before building structures on top. Especially when drawing foreshortened forms. Hope this helps. Keep it up!

Overall there is good movement in these, but some do feel a bit tight. How are you applying your lines? Do you find that you're making short and dark lines on average? The way that you hold your pencil, using your wrist vs using your whole arm, and the pressure that you apply when drawing your lines can all affect the looseness of your drawings. It's a good practice when working with rhythms to stay light and make long lines, especially when starting a drawing so you can indicate the overall gesture. Your anatomy is looking good, I really like the one on the second page in the top left.

I think the basic essence of the animal are present in your drawings - line quality and everything else will come in time. At least that's what I am constantly told by my peers as I just started this drawing journey too