No, system updates can't be undone. Once you've run the update, the old firmware is 'gone'. Running a system restore or formatting system memory, will only provide you with a clean version of the updated firmware.
Chat with our AI personalities
You can't undo it.
I doubt it. Maybe if you reboot the system, otherwise no.
It's not possible, I did a system update - formatting the system doesn't remove the updates just all userdata.
Just updates your DSi to the latest firmware.
After you update the DSi XL, there is no way in removing that update.