Hi @paulsmithy welcome.
You should really only use it if you cannot move the projector closer to the wall. As you lose some resolution/sharpness.
This is the best way, yes.
No need to do this. Different content has different aspect ratio. Just match the projector’s home screen, all other content will follow.
Yes.
Yes, red means charging, blue means “not charging” (not necessarily full, it will be blue during normal usage too if the charger is not plugged). Check this for more INFO: What do the different LED colours mean?
Yes it’s an expensive 4A charging + usb-c video cable. So if you don’t use usb-c video, you can get another 4 ampere charging cable (high power usbc cable).
But the best way probably is to use a power extension cord and plug the supplied adapter to it. Then use the supplied cable, avoiding the trial-n-error hassle of finding the right cable.