In order to hard reset a Bird S668, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Bird S668 device will be brought back to the default configuration of a brand new device.
1. Turn off your phone.
2. Type in one of these sequences: *#77218114# or *#881188# or *#94267357# or *#9426*357# *#19912006# *#118811# *#3646633#
3. Allow your phone to restart. Done, the hard reset is complete.