For URLs just follow the instructions from my original answer:
When you uninstall JoomSEF, all the tables in your database starting with jos_sef will have the _bak suffix added, so no data are lost. When you install the older version again, just restore the configuration.php file from the backup, and in your database delete all the tables starting with jos_sef that don't end with _bak, and then rename the ones with _bak so that you remove the _bak suffix.
Of course don't forget to make a current backup of your website (eg. with Akeeba Backup) before doing this.