This is a VERY old CRT rear projection television that is not high definition. It is not worth spending any time or money on it if the image is unusable at this point. The dials and knobs should only be adjusted by a professional who knows what they are for and there is no 'zero' or 'reset' button. That's what digital displays do. CRT is a analog display format and the knobs and dials adjust all alignment.
You certainly are free to play with those dials and knobs as you are unlikely to hurt anything and you may be able to get things to look better than they do now. You should search up YouTube for information about alignment, convergence, and adjustments of CRT projectors. Front and rear projection should have similar setup procedures, but every manufacturer will be different about what they offer and setup.
It has been about 17 years since I pulled my CRT projector off my ceiling. It has been a good decade or more since CRT production was stopped completely.