I have an app and I want to know, if I want to provide a paid version that's ad free, do I have to make a totally separate app? Like one app that has ads, and then do I have to completely remake the app without ads?
Probably the best practice is to make a full version of your app but limit the functionality. Then you provide in-app purchases to enable the functionality that was limited. You can do this all at once or in parts.
For example, a game where level 1 is free, levels 1-5 are $0.99, levels 1-10 are $1.99, and so on.