ZTE F850 hard reset:
You can reset your ZTE device's password: Turn off your phone, then turn it on. Select emergency dial. Input *983*987# in emergency dial-up pad. It will restore factory settings and your personal data will be erased.
Select SETTINGS, then
Scroll Right to access the Handset Settings.
Select: menu 8. Restore default settings: Restore to original factory settings.
default security code = 0000