1) I tried the shortcuts and it seems many win + keys are taken by windows and the OS doesn't let other apps use them.
win key + e opens my computer, I'm not sure what win key+ home does though.
I also tried a few others, and some do works like win key + a or win key + c.
2) to change rings, you need to middle mouse click or do you mean rotating the icons?
There is a bug on laptops that make SliderDock behave strangely but this should be fixed with the newest version (v1.22).
3) I'm not sure why this problem happens for you, on my pc it works correctly. Are you sure SliderDock isn't stuck under the browser or does it not appear at all, sometimes always on top can be a bit temperamental and I haven't found a way to fix this yet.