So in the case of the Nuron 5230, specifically, do you believe you would have success
in downgrading the firmware with any of the commonly available hardware or software or such options or not in a corresponding manner?
Why (technically) is it so difficult anyway? I can think of only a few possibilities for this:
A: that version updates are always sent out encoded as a set of incremental memory patches to transition from some specific older version to some newer version without actually having the complete 'new' version information available, so it would simply lack the data to go from Rev F to rev C since there would be no such differential patch data published, and you would not have the entire 'Rev F' image available to flash regardless of your starting version.
B: The update loader runs with the cooperation of the flash loader software in the handset, and the flash loader / upgrader software in the handset will just check the version of the loaded software versus the version ID of the incoming software, and it will refuse to load older version software. To change this one would have to either corrupt/delete the existing software or its ID code on the handset and hope that a full 'dead phone' reflash could write the new image, or one would have to alter the presented version data ID tag from either the existing or new software so that it appeared that it was a suitable upgrade regardless of the original version numbers.
C: The only update loader software available was actually written by Nokia or other parties that simply refuse by design to let you downgrade, although there would be no technical reason why it could not be otherwise. The mechanism of the check and the options of bypassing it would be as in (B), or, of course, just having a differently programmed firmware updater loader program which was not restricted in what it would permit loading.
D: Nokia's own sofware is created to arbitrarily deny downgrades in most cases, and 3rd party software updater / loader programs either do not exist or are really incompetent enough that they don't really understand how to fully and correctly reflash the unit in any but the simplest of cases, and so any given upgrade or downgrade may fail if they don't totally update the code and corresponding metadata properly. In this case it seems like we just need better 3rd party version loader / updater programs if there's no technical reason they shouldn't be able to read any firmware image and upload it successfully.
Anyway it is a bit strange since I've heard of people talking about 'dead phone' flashing etc. So that would usually imply that you could have a totally corrupted existing flash and successfully reflash a new ab initio version onto it regardless of what version had been previously loaded. Only if the phone wasn't completely zeroed / formatted could any trace of the previous version be left to matter relative to what the new version might be. Since the downgrade is still complicated, it must be that either the dead phone reflashing must not work fully in the case of missing firmware/metadata, or that the new firmware simply isn't able to be loaded without some kind of contextual data left on the handset from the previous version as in (A).
It is disconcerting that there should be such a problem, though, and it seems like
the origin of it should either be corrected or at least clearly documented so that it
is not so unclear.
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