How do I make the iPhone app emulator retina-size? I'm developing an iPhone app and the only device I have for testing is an iPad 2. I can run the app on the iPad and it will use the internal iPhone emulator (or whatever it's called). But the display ratio is that of the older iPhones, not retina-size (see this, I need the last version). How do I change the aspect ratio?
There is no option to change to retina or 4" screen size for iPhone apps running on the iPad.  You should use the simulator in Xcode instead (or get another device).