Chosen Solution
I was have a problem with error 21 when restoring. I get a new battery, but she was not working. I buy again new battery. When i connected the battery, now i see (i don’t turn it on) mobile is so hot in marked area.
that is the loudspeaker that sits on the charger port flex cable, you could unplug the charger port and try to turn the phone on, and if that works you may need a new loudspeaker/charger port
