To return from fullscreen, I assume you can set a keyboard shortcut under Control Panel/Bluetooth Keyboard/Shortcuts, just like the n810

These can be edited to any key combination you want.

Personally I hate the silly design aesthetic of no buttons on a sleek face of a phone. It's pure form over function, good tool design makes the function of the tool it's beauty. But phones seem to be sold more on sex appeal, than usefulness.