Im a tech support of 1 of the prepaid US telecom, everytime a customer will call about their phone got hard reset, I always say It is a dead end. And would advise my cx to contact google and follow their password recovery troubleshooting. Or last resort is send their phone to the manufacturer then let them flash the rom of their phone. Like Iphonei think once the phone was factory reset and cannot remember pw. Its like throwing away a $400 phone.