Back button navigation

[Hacklor]

As a developer I want to make sure the back button works properly, so that it will improve the experience of the users when navigating the app

I hate it when the back button does unexpected things. This user story is a reminder to check that
and improve when necessary. The back button should not be a stack of all the screens the user has
navigated to before. But a logical tree. This might require updating the navigation stack. In
Android the back button can also be used to go back to the phone's main screen when you are in the
Main Screen of the application.

How does this work for iOS? Swiping left and right?