A:AnswerYes, I use it across every major OS without issue.
Obviously formatting will come into play. But the drive is recognized and can be used as any other drive.
A:AnswerYes I believe so, however, it MAY be optional. It's something called WD Discovery. It allows you to download and import videos and pictures from other applications such as OneDrive, Facebook, Twitter, etc.
A:AnswerNo, you cannot backup your iPhone here. You should use iCloud or some other cloud service for that. Ask someone at your local Apple Store or Best Buy to help you with that.