X6-00 Best way to format and reload everything

Question

What's the best way to erase absolutely everything from the phone, inlcuding firmware?
I would plug it into Nokia Suite once that's done, and download the latest version of the handset's firmware. 
After having tinkered with it for a couple of years now, downloaded and then deleted various apps, i find that it's running a bit slower, and whenever i check for software updates, i only ever get the same four, which i've been offered now for over 6 months without any change.  I suspect that the phone's update facility isn't working properly.
current software version on my X6 is V. 31.0.004
Lumia 720 on O2

Answer 1

use Nokia Suite to make a backup of the stuff you want to keep.
then go to Menu > Applications > Office > File Manager > open the E: memory, and from the options select to "format mass memory".
that will format the E: memory.
to format the C:, do the following.
switch off the device. press and hold the "green" - "red" - and "camera" keys and at the same time switch on the device, don't release them until you see the "select country" list.
(if you don't see the list, do it again.)
that way you will format the C: memory.
you can't erase the memory where the firmware is installed. you can only reinstall it using Nokia Suite.
those updates you keep seeing for months now, are the latest updates the device finds for the installed apps on your phone.
the updater is working as it should.
Greece Nokia X6 RM-559 v40.0.002