I'm not familiar with iphone history and capability, it's possible an older phone will struggle with it but worth trying before you buy something newer.
You definitely don't need a sim card in it provided you can go on wifi.
You do need internet and the app working at least initially because it has to be registered with DJI when you first get it. (I believe motors won't even start till this is done)
Maps are somewhat optional if you are in Line of Sight but still nice to have that additional indicator of exactly what it's flying over in real time.