to the problem of the rear camera. it is impossible to change the flash mode, the camera does not work. programmatically it does not solve anything, of course. Then I decided to dismantle the phone and look at the camera module. it is made on a separate board that is screwed to the base with two screws. and one of the screws was not properly screwed in. I twirled it and it worked. that is, the camera module thus contacts with the motherboard. photo on the screws indicated by arrows. But remember - if not sure - do not disassemble.