Yes, it’s a standard iOS gesture with no equivalent on Android other than implementations that apps try to come up themselves.
Not entirely: the standard behaviour of navigation on iOS is to allow swiping from only the left edge to go back. It seems that Instagram added the ability to swipe left from anywhere on the screen, not just the edge.
I don't use Instagram, but I'm not surprised that they've decided to "customize" that behavior.
Oh thank god. I thought for a moment there the chimp could figure it out but I couldn't.
pretty much every android phone now has gesture support