Any changes you make to your app or website, will be reflected in real time. The only updates that cannot be changed once you publish/build your app are :
1. Splash Screen
2. App Icon
3. App Name
To update these, you will need to create a new build of your app. Once you update the app icon, splash screen or app name, you will need to generate a new build of your Android & iOS app from the Download screen. Once the build is generated, you can submit it to the app stores. When users download your app from the app stores, the changes you’ve made to the splash screen, app icon, or app name will be reflected.