Updating Lightroom 6 to final version without overwriting catalog

Hmm, now I am wonder if I mistook your request. My fault for not reading correctly. I was assuming you were using Lightroom CC not lightroom 6.

Lets see if we can get an adobe employee to look into your situation. Maybe they will know why your updates are not taking.

Have you tried the cleaner and start fresh? As long as you back up your data, you can make sure you still have your catalog should things go sideways. The cleaner should not affect the data, but it pays to be safe.

Generally when updating Lightroom, if it does need to alter the catalog, it will tell you that it needs to be updated when installing lightroom's update. What happens is it creates a new catalog and updates it with your old catalog, leaving the old catalog alone. This allows you to use an older version of lightroom if anything to wrong.

When you are satisfied the new catalog is fine and lightroom is stable for your uses, then you can decide if you want to delete the old catalog or not. You will find all the catalogs together in the same folder normally named with the version number. To make it easier to find. Once you have done this a few times, it becomes very easy to find, next time there is an update.

If you don't receive a message during the update about the catalog, then you don't have to worry, it is using the same catalog and did not change anything.

I hope this sheds some light and did not make anything more confusing.