This does't make sense. If these functions are running on the main thread, there is no way that the application can terminate normally while your functions are running. This is because the events sent like applicationWillTerminate:
are sent on the same thread.
If your function is running on a different thread to the main thread, you will need to save some state information after each function completes, but you still have a race condition.
It might be better to check your application's state before running each function. For example, if you have a three step login/registration process with a server, you should query the server to see if the stage has been completed already before running it.
It's difficult to be more specific without knowing what you are doing in these functions.