Cure firmware is used exclusively on soft-bricked devices to re-enable Mass Storage Mode thus allowing for corrupt files to be deleted. A device is soft-bricked when it's unable to boot properly due to such a corrupt file not being able to be loaded by the system during the boot process (e.g. a map .img file, a voice .vpn file, a POI .gpi file, etc.). Your device is booting fully so cure firmware is worse than useless, it'd be counter-productive quite frankly. In any case a cure RGN file can't even be loaded because if there's a hardware fault preventing MSM then preboot will also not be attainable reliably.

As for this:
Spoiler: Click to see image

[Only registered and activated users can see links. ]

That 'error' was only because when you clicked the Updater.exe button, it can't run because it didn't see the device in preboot or maybe it's because of Windows UAC settings.