So I got it guys. Devices like A12, A22 and all those budget smartphones run on One UI core instead of One UI. The core is a lite version of original One UI & doesn't support some apps like these.
But you have two alternatives on Play Store, the Fine Lock and Nice Lock. These work exactly the same. You'll have to download apks of modules from the site when you have installed the app. Next install those apks & customize your device.