How disable installing apps

Year1917

Just found this on a other fourm can someone explain this to me

"Yes, remove the permission to install package to the target user by making the account a managed account, or hook system to intercept installation window and ask for a password or outright kill it. (What you are looking to intercept is probably com.android.packageinstaller.PackageInstallerActivity). Going to intercept route means you may need to block app stores the same way as they can bypass this if installed on system partition. It will still be possible to install over ADB or recovery if left unprotected."

Thanks

But I doubt that an app without root privilege could intercept the activity, com.android.packageinstaller.PackageInstallerActivity.

if your apps are installing or updating automatically then go to the play store app and off the automatic update option then apps will not install and update automatically until you will not do thanx

If you are instaling 3rd party APKs then you switch unknown source setting. If it is off then no 3rd party will instal on your phone without permission.
You can navigate setting here. Open setting >> Security section>> Unknown source.

If you want to disable installing apps from outside sources, just simply turn off the Unknown source setting on your phone (Android 7 and lower). If your device version is Android 8 or higher, you can deny permission to access unknown sources installation each time you're about to download APK for example. You can consult the post here.