Native android apps in Unity scene

Hello everyone, I'm new to Unity, VR and 3D development.
Using the command adb shell setprop debug.layout true (Show layout bounds) I noticed that standard android applications are built into the Unity 3D environment.

Are there any examples or tutorials of how to do the same?

I managed to get Surface from Unity and output video there using exoPlayer, but how to display my native android 2D application, how to render layouts or open completely side applications in my Unity scene and pass events of clicks?

thank you in advance for your help