Here are my attempts at the hand demos, plus some extra ones.

The proximal phalanx of the thumb really does not hyperextend backwards like that, though. Especially not when the thumb is also bent at an acute angle at the same time. ^_^'

Oh man, this is completely different from what I expected! I totally thought that the checkerboard pattern itself was supposed to represent an appealing value structure for a portrait. XD

Here's my attempt at the assignments.

Help! I can't find the posed 3d models of the handbones he mentioned at the end of the "How to Draw Hand Bones – Anatomy for Artists" video. I purchased the premium course, so I should have access to them. Does anyone know where I can find them? "premium dashboard"? They are not on the right side of the video.

Just start. The motivation comes from the doing. :)

Here are my attempts at Tammy Slaton. In the first thumbnail, I quite liked the head shape and the hair, but the face didn't feel right. In the second thumbnail, I felt the features were going in the right direction, but the elongated head shape was a bad call. I definitely felt the head needed to be rounder and smoother. So on the third thumbnail, I tried to combine what I liked about the first and second sketch into one. For the final rough, I enlarged the third thumbnail and worked it out a bit more. I think it's going somewhere, but I'm also finding it quite hard to keep a sense of structure without using formal construction and taking measurements from the reference. What do you think?

It would be awesome if we could also have a 3d model of the arm in the pronated position! And also with the elbow bent, both supinated and pronated.