Android Emulator: Installation error: INSTALL_FAILED_VERSION_DOWNGRADE It means you're trying to install an app with the same packageName as an app that's already installed on the emulator, but the one you're trying to install has a lower versionCode (integer value for your version number)
adb - Howto downgrade any app to the previous version without losing . . . No guarantees however: if the newer version changed structures in its databases configuration, you will end up with an unstable app – and later updates might fail (in those cases, use TiBu to restore the full backup you made originally – so make sure to keep that one safe)
Android error: INSTALL_FAILED_VERSION_DOWNGRADE Confirmed, this is the issue and the solution I've just created a simple shell script that does exactly this: adb uninstall <packagename> ionic run android until this will be incorporated in Ionic uninstalling a package that doesn't exist should fail silently and it does, so that's great
Android_Install failed version downgrade - Stack Overflow This happen when your installed apk version less than version by which you are trying to build apk For example you just upgrade your version and try to build apk with it but you already a installed apk in your device which was build by the previous one