A:AnswerYes it works with Xbox one. You can use any USB 3.0 storage device for the one. Just simply open box and plug it in to your Xbox and it will auto magically recognize it and format it for storage.
A:AnswerIt plugs in the USB port and shows up under My Computer as a plug in... I ran my iPhone into one USB and the storage drive into another and had no problem directing things to it. I'm can't see why you wouldn't be able to leave it plugged in and save anything to it.
A:AnswerYes you can as long as you get 2TB drive to backup that much space. It comes with USB cable so just connect to the front USB port and go the system settings to backup PS4 to the drive.