Is there a way to install iPhone Simulator 4.2 in Xcode 4.3 for Lion? I only can find how to install it in Xcode 4.2, but not Xcode 4.3 for Lion.
I have found a way to install iPhone simulator 4.2 to Xcode 4.3:
Follow the instructions by Parth Bhatt, but install the simulator in a temporary folder ('Developer' folder doesn't exists in Xcode 4.3).
Once installed, go to <tmp_dir>/Platforms/iPhoneSimulator.platform/Developer/SDKs, and you'll find a file named "iPhoneSimulator4.2.sdk".
Open a new Finder window and go to /Applications and right-button on Xcode, select show the package contents, navigate to /Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs, you will see a .sdk files, one for each iPhone simulator installed in Xcode.
Drag the "iPhoneSimulator4.2.sdk" file from your temporary folder and drop inside SDKs folder of Xcode package.
Restart Xcode and that's all (you can delete the temporary folder).
If your project has a Deployment target to 4.2, you'll have the 4.2 simulator available.
Go to "Preferences -> Downloads tab -> Components tab" and install what You need. At the moment it lets me download 4.3 and 5.0 simulators.
I think its not possible. You can just download and install the SDK provided by Apple
来源：https://stackoverflow.com/questions/9342701/xcode-4-3-and-iphone-simulator-4-2