Is it possible to clone a game, and make modifiactions to it?

I basically want to know whether or not it is possible to copy a mobile game and make it into a new game by modifying it . I want to be able to access , moderation tools and basically alter, things like charcters, events, in ap purchases etc. Alter it to make it different enough from the original and make it available to other users. The game I want to copy is no longer in the play stores and I want to change that.