It is true that the status bar should be automatically hidden for games.
A freshly generated empty game project and also the demo games like “Flappy Bird” should all be fullscreen when running on Android.
If you are using the V-Play Apps Components or use the import VPlayApps 1.0 somewhere in your project the status bar will be visible, as the status bar appearance can be set with the App Theme then.
Are you maybe using V-Play Apps somewhere in your game project?
at the moment we do not provide any setting to hide the bottom navigation bar.
If you absolutely need that feature, you can add it by integrating custom Java code -> this requires to go over C++ and JNI though. (See here to learn about Integrating C++). However, we recommend to always have the home and back button accessible as it is the main navigation for the device.