There are some features of iOS apps that don't work from the iOS simulator, requiring testing and debugging using a real device. To run an Xcode project on an iPhone or other iOS device, select the device as the "Simulator" in Xcode and unlock it to allow app installation. Troubleshooting common errors such as signing issues, locked devices, and busy iPhones can be resolved by resetting location and privacy settings, unplugging and plugging back in the device, and waiting for a short period of time. With these steps and tips, developers can successfully test their iOS applications on real devices to ensure compatibility and functionality.