Xcode 4.3 Release was released on 12 Feb 2012 and requires macOS 10.7+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/xcode_4.3_for_lion_21266/xcode_43_lion.dmg.
Release notes are located at https://developer.apple.com/library/content/releasenotes/DeveloperTools/RN-Xcode/Chapters/Introduction.html#//apple_ref/doc/uid/TP40001051-CH1-SW699.
The SDKs it contains are:
- iOS 9A334
The compilers it contains are:
- clang 3.1 (Build 318.0.45)
- LLVM-GCC (Build 2336.9.00)