Yes, Samsung Gear Fit2 Pro can be used with any Android or iOS devices with Bluetooth connectivity of 4.2v or higher.
Yes, you can receive text and even can respond from the watch with some pre-programmed responses. You can see the call alerts but you will require either Bluetooth headset or the actual phone to talk. There is no speaker or mic in this band.
Yes, Samsung Gear Fit2 Pro does have the heart rate monitor.
Yes, Samsung Gear Fit2 Pro does have the GPS tracker.