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kotlinlang

Where can I find info about which firebase project is connected to my app? Thank you very much in advance.

Hahahaha
Well I can say this one is also not kotlin and recommend you to use threads for answering your doubts and providing more information

Now coming to your problem
When you register an app to firebase you need to set package name and upload sha fingerprint of your app and then add SDK of firebase and include Google json file in your app
You can go to project setting in firebase console and there will be a list of all iOS, Android and web apps attached to that project.
So to detach it you simply delete your project there or remove any individual app, also if you included Google APIs console them you need to check there as well