I thought it it a official renew phone, since the language is France and there are several apps left in the device. So the first step is restore factory setting:
1) Setting->accounts->Backup and reset ->Factory data reset ->reset device
2) First press the power button on the side of your phone to turn it off.
- Now hold down the Power, Volume up and Home button at the same time for about 10 seconds, check out the screenshot below.
- Release them when the android logo appears on the screen.
- This will bring up the reset menu.
- Use the Volume up/down buttons to navigate the menu and the power button to confirm selections.
- Now scroll down and select Wipe Data/Factory Reset.
- Now select Yes – Delete All User Data.
- Lastly scroll down and select Reboot System Now, and let it go to work!
Pull out the developer options.
Setting->More->About Device: tap build number 7 times. it will show you are now 4 steps away… after you tap 3 times. Then after you are done, go back to settings you ‘ll find developer options.
If you tap the “Android version” item repeatedly and quickly, you get this Easter egg on the screen.