The app and most of the functionality are free, however there is also a Pro version which lets you create unlimited habits, set themes, lock the app and more. The Pro version is $2.99 one off.
The app works on any iOS device running iOS 13.0 or newer and any macOS 11.0 or newer. This is a universal purchase.
It's important to understand that there are no shortcuts, but this app will help you build the right habits and provide a framework for sticking to them and understanding the psychology behind how our minds for habits in the first place.