Just wondering is there a hotkey for only render view.
Also wondering whats the hotkey for the default cube screen?
I am familiar with the numpad keys and screens.

F11 open render window if this is what You had in mind.
Ctrl+n in object mode loading base setup just like closing and opening blender again. Or if You want to go back to factory setings file–>load_factory_setings that will load the base cube scene( it will not save anything )

I meant hotkey for : N-Display- select only render
And hotkey for basic cube view but I was just wondering.