Open the Settings app.
Press and hold the Power button and select "Power off." If the phone is frozen, press and hold the Power button for 10–15 seconds until the screen goes dark. How to Hard Reset XIAOMI Redmi S2
Hard resetting your Xiaomi Redmi S2 (also known as the Redmi Y2 in some markets) is the most effective way to fix software glitches, remove forgotten screen locks, or clear out data before selling the device. Open the Settings app
The device will begin the formatting process. Once finished, you will see "Data wiped successfully." remove forgotten screen locks