A:AnswerIt does have a built in GPS allowing you to leave your phone home and still track your run. It also has a bit of storage to hold music so you can stream to your Bluetooth headphones - all without the need to carry your phone.
A:AnswerYes you can set the display to be always on. This will kill your battery fairly quickly so I wouldn't recommend it. Having it turn on when you gesture works fine and saves the battery when you're not actually looking at the screen.
A:AnswerIf you're sporting an iPhone running iOS 9 or above you'll be able to use the Gear Fit 2 (not the original Gear Fit 1). That's every iPhone from the iPhone 5 onward.
A:AnswerI was just outside working in the yard and go an email notification. My phone was in my house on the charger, probably about 75-100 feet from where I was working.