Although it would seem crazy, if you want to follow along seamlessly, you should download the Blender version that is being used in the course. The version of Blender is in the end of no consequence, the knowledge is the same.
The skin modifier is a bit finicky, you can try to massage the vertices a bit, move them around and see things jump into place. Also change the root placement, that always helps out a lot. So basically extend the arms and when things get messy, try all of that.
