How to prevent navigation bar from being hidden, globally? I know I can set some apps to not hide the navigation bar. But I would like to globally set that it should be shown by default. My Android is not rooted.

Basically I want the old behaviour back in Android 4.0 (Ice Cream Sandwich) where it was not removable unless you root the device.  However, I don't mind being able to allow it to hide the navigation bar on a per application basis.
Normally phone have navigation icons or bar so to hide you can have full screen mode/(depends upon brand its  name changes) under it their will be settings to turn on full screen mode to all apps individually.so u enable(no navigations)/disable(with navigation) them.On turing on full screen mode no navigations will be there.you may have gesture navigation or swipe to show again the nav bar.in samsung devices there is an advanced option in navigation bar settings to show or hide bar