Adobe - Archived Flash Player versions
Adobe - Adobe Flash Player Distribution
Adobe - Adobe Flash Player Administration Guide
Adobe Flash Player as msi-file has some tips for installation of the MSI version in a company setting.
After removing a newer version of Flash Player an older version can't be installed because the setup of the older version blocks you from doing so.
The workaround is to delete the SafeVersions key in the registry.
On 32-bit systems: HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\FlashPlayer\SafeVersions
On 64-bit systems: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Macromedia\FlashPlayer\SafeVersions