Blender 2.79 or 2.8 Aug 22 daily
* Huion 221 Pro Pen Display "SHIFT" hotkey does not work with any version of blender. This is a known bug.
1. No idea, I thought it was quite visible by default but that could just be me. There may be some settings in user preferences but better someone else answer that one.
2. Strange that "z" wireframe doesn't work even in 2.79? Alternatively you can enable backface selection by toggling it on and off. I don't know the shortcut but there is a button on the bottom bar in edit mode. It's right next to the vertex/edge/face selection buttons. On the left I believe. Sorry I can't remember exactly off the top of my head but it's in that general area, just hover over the buttons to view their description.