[wesk05]

3) Just for info here. Android Lollipop on AML S8xx/S9xx devices switches resolutions and refresh rates for 720/1080p <---> 2160p Automatically, but it has a 1/4 screen display issue when doing so. I've also fixed the video upscaling 1/4 screen issue when using versions OpenELEC / LibreELEC Kodi.

4) More info pls. Do you mean the Shield needs better quality upscaling ?

3) I based my answer on what @Koying and others have been saying. I think native Android doesn't have resolution switching abilities, but if you hack it you can get it.
4) Yes, hardware based upscaling can be improved. I think @Koying has added some advanced HQ scalers in SPMC. I will have to check on that.

I forgot to mention this:
9) On 3.2 update, refresh rate switching defaults to RGB. It overrides the color space setting (YCbCr, RGB).

Regarding @Bill4's comment about bit perfect audio output. You can get bit perfect output for 44.1, 96 and 192kHz with players that use the native audio player. It just doesn't work in Kodi/SPMC. I am not sure that you can get bit perfect output for 88.2 and 176.4kHz from Kodi on any OS.