General process for getting license keys for previous versions:
-Just go ahead and buy the current version of whatever you need.
-Try the license key anyway - sometimes they work. The general rule is that they work for the current and the previous release.
-If not, call Customer Care at 1-800-721-3934. Ask for a license key for a previous version.
-Document both the current and the newly downgraded license keys! You'll need the new one if/when you ever upgrade.
Hope this helps....