Gotcha, if you can't boot into download mode , might be hardware issue.It is true that it is very old and I also have a new phone, but I do not want to install the root or system modifications on it or store viruses on it, so I want to revive that phone, so I consider it like a dangerous mission phone .
It might be but in order to correct a software issue you would need to get into download mode which you can't so it can very well be replacing hardware to fix it .No its software
can usb jig turn on phone
Also make sure the volume button not sticking if still same , it would have to be opened the phone and inspectedOK Thanks