Purposes: security, regulatory compliance (payment/data), anti-theft, and to prevent tampering that could compromise transaction security.
If the shade is blocked, try a "long-press" on the power button and look for any settings shortcuts. sunmi v1 unlock
Unlocking Your Sunmi V1: A Guide to Greater Device Flexibility The regulatory compliance (payment/data)
Once identified (usually something containing "sunmi" or "kiosk"), disable it using: adb shell pm uninstall -k --user 0 [package.name]. sunmi v1 unlock