There are various solutions for performing hard reset for TECNO Y4. Note that hard reset will delete all data that your device contains including apps ,pictures, contacts, messages, etc.
METHOD 1
Turn on your phone and navigate to setting icon.
Scroll down to the last menu at the bottom.
Click “System.”
Select the option labeled “reset options.”
choose “factory data reset” option.
Tap the last “reset phone” to confirm you want to erase all data.
Enter a correct pin or pattern and select “yes erase everything” to continue.
Congratulations you are through! Wait your phone to restart and complete the initial setup.
METHOD 2
Power off your device
Hold volume + power key altogether
Use volume up key to go to “recovery” and confirm by pressing the power key.
Press power and key once when the android robot appears and you will be taken to android recovery screen.
Wipe data/factory reset by using volume down key and accept by using volume up key
Choose yes and confirm by using volume up key
Select “reboot system now” and accept by pressing the volume up button
Congratulations!!! You are done. Wait for your device to boot