Two questions:
1) Can Xcode 4.3 work on Mountain Lion?
2) If I upgrade Xcode to 4.5 on Mountain Lion then would I be able to support applications that were running iOS 4.3?
I believe if I upgrade to xCode 4.5 on Mountain Lion then I should be able to target old applications running iOS 4.3 with Non ARC code.
I guess it depends on the deployment target setting. In Xcode 4.5 it shows the deployment target of 4.3 as the oldest.