For our sideloaded application we need to disable the user to start the UWP application after install or update.
For your requirement, we suggest your add splash screen for the app. And store current app's version to LoclSetting, when you launch the app please compare current version with LocalSetting value in the splash screen, if they are different, you could hidden DismissSplash
button that make app will not navigate main page.
public static string GetAppVersion()
{
Package package = Package.Current;
PackageId packageId = package.Id;
PackageVersion version = packageId.Version;
return string.Format("{0}.{1}.{2}.{3}", version.Major, version.Minor, version.Build, version.Revision);
}