How to block from sideloading apps (ipa) in iOS devices.?
Without the device being jailbroken or having a development provisioning profile installed, there's absolutely no difference between an app installed via the App Store or via "sideloading", except that one might be able to install an old version of an App Store app. Or possibly an app which the developer removed from the app store by choice. It's simply not possible to install any app that's not originally from the app store via "sideloading" without it being configured for development as all applications must have a valid App Store code signature. If you want to block installation of all apps, you can create a MDM profile with Apple Configurator with this restriction.