Xcode 4.2 Release was released on 12 Oct 2011 and requires macOS 10.7+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/xcode_4.2_for_lion_21264/installxcode_42_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-SW713.
The SDKs it contains are:
- iOS 9A334
The compilers it contains are:
- clang 3.0 (Build 211.10.1)
- LLVM-GCC (Build 2336.1.00)