Changing google Password
If you perform a factory reset on the phone, do not change your Google Account password. Thank you to a new Google security feature added to new versions of Android, changing the correct password before resetting the device will result in an irreversible blockade for 72 hours on your device.
Android 5.1 (or earlier, depending on your OEM), Android comes with an integrated device protection to help keep your phone safe in case of flight characteristics. One of these functions, the factory settings protection must sign the phone with the Google account you’ve used to sign in. The idea here is, if a thief steals your phone and then immediately reset, the reality will not be able to use it unless you also have your logon account information.
“Well, what is to stop a thief password reset and use it to access my phone?” Good question! Since the phone can receive their codes of two factors and emails, access your phone, it is easy to reset your password. For this reason, if someone changes the password for your Google account, then immediately reset the phone, Google assumes a thief has your device and start a 72-hour strike.
The idea that the blockade is that it gives you time to recover your phone if it was stolen before a thief can access. In case you really need to do a factory reset on the phone and change the password, there is a simple solution: make the first factory reset. Once you’re connected to your new device, you can change your password just fine. If (and this is probably even safer): Change your password, then wait at least three days before resetting your phone.
Android Police have also noted, if you reset the unit to sell, you must manually disable the lock screen and delete your Google account in full. This is not only one of the reasons more should lock the screen, but in so doing prevent the device that requires a login account after a restart.