Saving/downloading current firmware before updating? And how to revert

@OnlyTwo, aren't you refering here to the specially crafted .RGN system image file that has to be flashed to the unit using an external updater program in case of a fully non-responding unit?
I have used many Edge models (800, Touring, Explore, Explore 2) and never had problems with rollback to an older firmware version using the normal GUPDATE.GCD file that comes from Garmin while using Garmin Express. So, I don't understand what's going wrong with @8320953's Explore.

In your starting message you say you are on version 5.10 and consider to eventually upgrade to 5.40.
Later on you tell that you have problems downgrading to 5.10. Did you upgrade to 5.40 in the meantime? If not, you are still on 5.10 and then I can understand that supplying a 5.10 version GUPDATE.GCD will have no effect.
By the way, it is normal that the GUPDATE.GCD file is removed from the unit after processing. You don't have to - or should not - make it read-only.

Says its been deleted by the owner

bikepc01Yes sorry its a bit confusing. I have upgraded to 5.40 on my device.

My friends device has strang issues so I wanted to try to downgrade to 5.10(its on 5.40)

Former Member non of those links work...