How do I install Xcode 9 without updating macOS?

Question

Does anyone have any idea to install Xcode 8 OR Xcode 9 without updating macOS?

I want to update my Xcode 7.1 to Xcode 8 or Xcode 9 (or 9.1) Beta.

But it is

Answer 1

Xcode 8 will work on OS X 10.11 (El Capitan) but the apps you build with won't, because the only SDK available is macOS 10.12 SDK, i.e. macOS Sierra's.

From release notes:

Compatibility

Xcode 8 requires a Mac running macOS Sierra 10.12 or OS X El Capitan 10.11.5 or later.

Xcode 8 includes SDKs for iOS 10.0, watchOS 3.0, macOS Sierra 10.12, and tvOS 10.0.