How to communicate between iOS and Unity3D?

We have small interactive activities and a Native loader that loads all unity activities. We want an issue in communication between loader and activities. When the activity is opened from the loader it should show back button that will move us to the loader again. But when an individual activity is opened directly without a loader as an app it shouldn't show the back button.

Now the problem here is we don't get to know when the activity is opened from the loader or directly.

Please help use to find the proper way of offline communication.