A friend of mine owns this tablet and has entered the password incorrectly too many times and now the device is locked asking for a Google account. Unfortunately the Google account password is forgotten.
I figured the only way would be to factory-reset the device from the Recovery mode but when I enter the recovery mode (by holding Vol Down + Power Button) it reboots the device after a few seconds in recovery screen.
Now I'm stuck and have no idea what else to do. The tablet model is S7-931u.
I had the very same problem for like 4 months. And finally, in one day, the problem was solved. Follow these steps:
Switch off the device.
Press power button + Volume up button until the device is switched on (followed by a small vibration).
As soon as the device is switched on, let go of the power switch but keep pressing the volume up button.
After a few seconds, a screen will appear showing a green android symbol with rotating gears. When this screen appears let go the volume up button and keep pressing volume down button.
Hold like this for a few seconds. till a big green 'OK' appears on the screen.
After this the device re-starts automatically. It may take some time. After this, it'll be like you're switching on your tablet for the very first time. You have to provide your GMail address (optional), name, system date and time etc. All the apps and files that was previously in your device, will be gone.
locked-outtag to your question. Its tag-wiki contains further information. Especially take a look at Cannot unlock tablet as have no internet connection?