How to install iOS 4.3 Simulator on xCode 5? It's required to test the application on Deployment Target 4.3.
Firstly, there's no official way to add the iOS 4.3 simulator. You may be able to hack it somehow but I don't know how and I wouldn't recommend it.
Secondly, if you really want to support iOS 4.3 you need an actual device to test it on. The Simulator is not 100% accurate and it certainly doesn't mirror the performance of a real device. If it existed, using the Simulator would be a good "first pass" but it's not a substitute for the real thing.