How to test your app while not effecting active users?

I am soon ready to release my app on the play store but I would like to know how can I edit/add features/update my app without affecting my users. For example if I decided to add or remove something from the server I don't want the whole app to crash on the users. Basically running a clone where I can try out anything I want and it stays separate from the original app. How do I do that?

I am really sorry if I confused you all and my English is not the best.