A:AnswerYes it is compatible with iOS. Just double check the spec list on the product. Phones usually have a shelf life of 2-3 years. So after that, you should have a newer device if you’re concerned with compatibility.
A:AnswerNo it does not track distance using a GPS. It tracks pedometer steps. I wear a GARMIN with my Fitbit and the pedometer on the Fitbit is pretty accurate. Input the correct stride to get the most accurate distance.
A:AnswerI had this happen to me once and it turned out it was because I bumped a button in the settings screen when I was checking the battery level. If you hold down the side button you can access the settings screen and there’s a button that allows you to turn this feature on and off. I believe it looks like a lightbulb?