Force to install a software on older macos version
Your best bet is a Virtual Machine using VMWare or Parallels, as historystamp suggested.

In most cases, if the app won't install on a given version of macOS, there's probably a good reason for it. I wouldn't be surprised if it failed to run even if you managed to get it running.

That being said, if you are determined to try, there are two free tools to help:


unpkg
Suspicious Package


Both will let you “extract” the contents of a package file. From there you can move them into the proper places and see if it runs.