Maybe nitpicking but a lot of people outside the US have no idea how many inches there are in a foot, and have no reason whatsoever to know it. Personally I automatically dismissed 30" as an odd value and didn’t notice until writing this that it’s actually the same as 12 * 2,5. Local US measurements isn’t really a SketchUp question.
I’m not really a fan of this phrasing. The layer isn’t a sheet or a box or any other kind of place in the model, but a property of the entity. It’s the the layer that is assigned to the group, not the group that is assigned to the layer. I think this distinction is important to understand how SketchUp layers are different from typical layers.
On Windows autofold is controlled by Alt, and there is no Option key.
One think I really apriciated though is how the time left counter only updates when you go to the next question, not once a second. I can never read text and concentrate properly when something is constantly flashing in the background.