I just downloaded Xcode 4.1 that comes with 4.3.2 sdk.
I have built a little app and what to test it against 3.X.X and 4.2. Is there any possibility of downloading the sdk's separately and install them? I mean without Xcode 3.X, etc...
You can select which versions of the iOS your app is suitable for. Appropriate versions of the simulator will appear.
You can set it in Xcode -> Targets -> Build Settings -> Deployment -> iOS Deployment Settings Set that to iOS 3.0 and launch appropriate simulator.