None of that is a problem.
You can't "update" FEF because you already have a newer version. The one included in the dev release you installed came after all other published versions. FEF won't let you downgrade it. However, this is NOT a problem, it's how it's supposed to work.
Likewise, FEF doesn't let you uninstall it when there is other software depending on it e.g. Akeeba Backup, Admin Tools , Akeeba Ticket System and a number of our other software. If you uninstalled FEF it would break all that software.
So, you tried to do two things which would have broken your site and our software declined to let you do that. Therefore it worked just fine.
If you got this message while trying to update Akeeba Backup or Admin Tools please read the entire message. It tells you that if you see an error about FEF or FOF not being updated IT IS NOT AN ERROR AND YOU CAN IGNORE IT. (I have to stress this out, sorry) We'd really prefer it if Joomla would simply NOT show this message when we tell it not to downgrade or uninstall an extension but it's not under our control, it's under Joomla's control.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!