Aren't all the apps in Windows Phones full screen?
With the auto-hide option enabled*, you can simply swipe downwards from (not tap on) the top of the screen to show the "status bar" together with the notification center. Some apps have the option to permanently show the user the status bar, and that can be found (if available) in the app settings.
Similarly, you can show the navigation bar by swiping upwards from the bottom of the screen.
*- Clarification: this pertains to the navigation bar at the bottom, yet the next clause pertains to the "status bar" on top.