Modify & Rebrand Mac App/Update a game

I want to take some source code for an exiting Mac app and create an app with a different purpose. That means adding some features, changing the app name and adding a new icon. The app will have some restrictions. It will have an IAP that removes those restrictions. I also need it uploaded to my itunes connect I also want to update a Mac game. I will be changing the name and icon of the paid and lite versions of the game.