If this is for Internet Explorer: as of Windows 8, Microsoft embeds Flash Player in Internet Explorer and all updates are released by Microsoft via Windows Update. Therefore, to revert to a previous version would require uninstalling the 'Internet Explorer Update for Flash Player' (or similarly named update) from your system until you get to the version you need.
A list of all Internet Explorer Updates for Flash Player is listed here Microsoft Security Advisory 2755801. Each update contains a KB number which corresponds to the update installed on your system.
Please note that running older versions of Flash Player is not recommended due to older versions not containing any security fixes implemented after the release of that version. Also, several browsers block older, non-secure versions of Flash Player. Therefore, even if you install an older version you may not be able to use it.