The endpoint where monitoring data has to be sent to is in the configuration snippet added to the gradle script (Android Studio) or the Info.plist file (Xcode). If the domain name of the Active Gate changes this also has to be changed when building the mobile apps. Also mobile apps with old configuration won't be able to send their monitoring data to the AG if its domain name changed.
You should create AG and define public endpoint. Then after adding DT binary into your apps you are putting there some configurations, one of it is address od cluster active gate. You can build such app and test it on device (actually developers can), you should be able to see visits in dt. If there all will be ok, put apps into stores and you are good to go 🙂