We don’t enable you do this, as the name is used for the database, etc, but 1) you can clone the app and then chose another name 2) once you’re on a custom domain it won’t be visible to the users.
You don’t set the “Content Type” on the Index page to be User. At the moment it is expecting a User to be passed to it. Chances are you don’t want that on your starting page.
You remove the debug mode, which is only there for dev anyway.