If you want to change the domain name of your app, you will need to reconfigure the options in BuddyBoss App. Then, you can add the domain name on your Google and Apple Developer access. No need to unpublish the old app.

To start, you will need to reconnect your BuddyBoss App license to your new domain name. Here is the tutorial

Then you need to reconfigure your iOS and Android App: 

Configure Your iOS App

Configure Your Android App

Once the latest version is out, they can switch on the 'minimum build version' to force their users to update the latest app.