How To Unlock Android Device Forgot Password..

Unlock your Android device using Android Device Manager (ADM)

1. On a computer or other mobile phone, visit: google.com/android/devicemanager
2. Sign in using your Google login details that you also used on your locked phone.
3. In the ADM interface, select the device you need to unlock.
4. If it was successful, you should see a confirmation below the box with the buttons Ring, Lock and Erase.
5. You can check you Device by Click on 'Ring' Button
6. Click ‘Lock’ button
7. In the appearing window, enter a your new  password. 
8. Now click ‘Lock’ again.
9. On your phone you should now see a password field in which you should enter the password. This should unlock your phone.
10. Now, you can change password again of your device
11. That’s it!

To Unlock Android Phone  perform a Factory Reset, take the following steps:

1. Turn off your Android device.
2. Press and hold the "power", "volume down", and "power" buttons simultaneously. ...
3. Release both buttons once your Android device is powered on.
4. Scroll using your "Volume up and down" button until you find the "Factory Data Reset" option.