1: Yes, you must have a Mac to do Xamarin.iOS development. Then in the Menu bar go to 'Hardware', 'Device' and select the same simulator as the one that is running on your Windows machine. Now, iOS developers can build and debug iOS applications in Windows machines, using Visual Studio.
If you're using Xamarin/Xamarin.Forms and the standard then this code is fully managed code and will not communicate with the local OS to discover the proxy settings.