Like to repeat, the older version of this add-on used plain files as a storage. In the meaning of storage, versions of Premoderation add-on do not cross.
As about the generic forum, you can use the same DB for tests, but I suppose, the newer version of your forum still needs the most recent upgrade for DB. However it all depends on your current version of the forum. I did upgrade of the default DB rarely, so it is quite possible that the older forum still could work with the upgraded DB.