I've never noticed a "Get a previous version" option. Do you have a custom build of Firefox, or a version someone has packaged with add-ons??

Have you tried the steps in this article: Recover lost or missing Bookmarks

Whatever rollback process you used, you might have multiple personal settings folders, also known as Firefox profile folders. You can check the standard location by pasting this into the Start menu search box and pressing Enter:

%APPDATA%\Mozilla\Firefox\Profiles

If you have multiple folders, the dates should help identify your current and immediately previous folders. These articles might be helpful in loading your earlier profile into your current version of Firefox and/or copying over data:

• Profile Manager - Create, remove or switch Firefox profiles
• Restore bookmarks, passwords, and data from an old Firefox profile

You should update your current Firefox 12 version as soon as possible to the current Firefox 17 release.

The Firefox version that you currently run is no longer supported with security updates.
It is important to update Firefox and add-ons to the latest versions to get the latest bug fixes and security updates.

You may need to do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox.

Your bookmarks and other profile data are stored in the Firefox Profile Folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

If you have submitted crash reports then please post the IDs of one or more crash reports that have this format:

• bp-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

You can find the IDs of the submitted crash reports on the about:crashes page.

• You can open the about:crashes page via the location bar, like you open a website.

See:

• http://kb.mozillazine.org/Mozilla_Crash_Reporter
• https://support.mozilla.org/kb/Mozilla+Crash+Reporter

See also:

• http://kb.mozillazine.org/Firefox_crashes
• https://support.mozilla.org/kb/Firefox+crashes