Into VR sample and button on Gear VR

So I built and deployed Intro VR sample to my Gear VR. Worked right out of the box!

Question - when I press Back button, screen fades to black. If I press it again, screen goes to pre-fading state and fades to black again. How do I make it fade once and do nothing else afterward ?

Also, how to make app to go to Oculus Global menu when pressing Back button on Gear VR ?

Thanks!