That’s a backlight ic issue in pcb.you have to change it

You will see two little white gums strips with black tap on bottom. You have to pull up those two strip so battery will come out very easily

If your lcd is properly fine then it can be a LCD Ic issue on pcb

You might check that front camera flex cable.there can be a damage also where war speaker connects

Bro check the small black cable near the battery connector.its for network. Make sure that it won’t torn or forgot to put back in place

That cable is for sim networks. You have to remove very carefully.if it will break then you won’t get a sim single on your phone

Yes you have to remove battery first otherwise it may cause a short circuit sometimes.so that phone can be dead also

That is gps antenna

Those 2 cords are for GPS antenna to send and retrieve signals

when its extracts the file in itunes it restarts again and again