So you're really far behind.  BIOS A02 is here.  After A02, you might have to do one or more additional intermediate updates to get to A14. Links for all of the other versions are available by clicking Other Available Versions on that same page. The page for each version says what it fixes/improves so you can see what they do. Updates are cumulative so if you can go directly from A02 to A14, A14 will have all the updates in the versions between A02 and A14. 
Dell Hello, I installed the DELL SUPPORT ASSIST app to check for any updates on my OLD laptop. I started checking for the updates (especially, since I have one driver I couldn't find any update for it). Then I found there is an available update for BIOS, I downloaded. After restarting my laptop, launching the DELL SUPPORT ASSIST again, I got the same BIOS update message, I downloaded it again! Then again the same happened!5 times I got the same BIOS update message!!In each time I updated! but still the same message shows up!attached pictures for more details.[IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE]
Dell Latitude E5420 Bios updating