Thank you for contacting the forum about your question.
You can press the home button on any android device and it will take you back to the home screen from any app, there is no need to restart the device.
The back button was disabled as a feature to prevent users from switching between landscape and portrait mode inadvertently or ending up in the app menu. The back button will take you back to the last few screens of the app until you reach the home screen, not always what you may expect.
I will add to the list of potential features for the next release of the app, the ability to enable the back button function.
Please let me know if you are able to successfully use the home button to leave the app.