The white version costs more because it already has software installed, such as Netflix, etc. I have and prefer the black version without additional software, which also minimises the risk and the software can also become obsolete or no longer compatible in the future.
3. actually only at least 30 cm away from the wall, but only in an emergency...because you only get an approx. 2 m wide picture from a distance of approx. 2 m, that's how I did it and directly on an abrasion wall without a screen the picture comes out pretty pin sharp, I'm absolutely satisfied so far !!! What I think is very important and makes a big difference to the sharpness and sound is the use of good quality cables (optical for sound and HDMI 4K UHD for picture), i.e. the thicker and shorter the better...I would not have thought that this really makes such a big difference.