You can download older releases of the Joomla! CMS by following these steps:
1) Sign up to JoomlaCode 2) Go to  3) On the left select the version of Joomla! you're curious about. 4) A section should expand out, select "Browse Releases". 5) You will be given a list of available downloads for that release. Download what you need.
Legacy Joomla CMS downloads are hidden to prevent accidental installation of unsupported releases or releases that have been superseded by later releases due to security issues or bugs discovered. It is always encouraged to deploy on supported releases.