You can make changes to your mobile app even when it is live (or published on the app store(s)) and these updates will reflect on your app in real-time.Additionally, any updates you make to your website will also reflect on your app in real-time.Note that the only changes that cannot be made once you publish your app are:
To update these two, you need to add the New App Version add-on product to your subscription. Once you update the App Icon or Launch Screen, you will have to release a new version of your mobile app on the app store(s).
You will have to update your app when a new feature or code version is released. Also, your app users will only be able to view the changes when they update their apps from the app stores.