Correct me if I am wrong:
You have tried more then 3 different RAM sticks. Two of them are supposed compatible, "If I were you I would eliminate the RAM problem". You took the MB out of the case & tested it with minimum settings "Exactly like Diego instructed". That didn't work also
You tried to update the BIOS via recovery method. Yet that didn't work.
This is an old board. So was it working before? or was it stored properly?
With all do respect, cut your losses & stop spending money. Try Diego's last tip. If that didn't work then you have a faulty MB.