This info for all people who dropped phones in the water. 1 Switch off device. 2 Remove SIM card with card holder. 3 Use hair dryer to dry your device. (Warm 80-100 degrees for 15-25 minutes.)
I do not think that the problem is in the update. it is possible that water got into the phone or you dropped the phone. You should ask some one with knowlege to open this phone and check inside.
i think you have bad contact with pins on charger or charging port on laptop, i sugest you use eraser to clean up those pins on charging port. Eraser helps me to remove oxides on contacts
i think you have problem with backlight on TV, try this -> turn on the TV and wait for the screen to turn off then take the flashlight and shine on the screen if you see the image it means you have problem with the backlight.
For micro soldering you must have a microscope. About backlight, you need view mother board in detail under microscope, in 80% you can find suspicious SMD components on board, and fix your Phone.