Hi, you can (A)
CTRTransfer /
region change -OR- (B)
CTRTransfer (Type D9) - CTRTransfer the 3DS firmware from EUR back to JPN.
If (A) standard CTRTransfer is done, reinstall the backed up legit tickets with
FBI in the later
sections II–IV, system update to the latest 11.13J,
repair the bricked DS(i) mode with TWLFix-CFW, and relist DSiWare games with the aid of
CTRTransfer (Type D9) - DSiWare CIAs & Saves.
IF (B) alternative CTRTransfer (Type D9) was followed instead, the
Instructions will contain all the necessary steps in what to do.
***
I don't know why anyone would want to
uninstall custom firmware. Even if you're looking to sell the 3DS, it's better to find a buyer who'll want yours already hacked. You're going to be kicking yourself if the uninstallation goes wrong, the buyer backs out purchasing your (now) paperweight, and you're now left selling it at a lower price to someone who's willing to fix it his/herself with the
ntrboot method.
Make sure the 3DS passes the (temporary no custom firmware)
Section I - Safety Test. The system tickets, system titles, and
SecureInfo_A|B should be fine when reverting to JPN without CFW. User profile setup with leftover EUR savedata might not work. This will have to be checked by renaming the
data folder to
data2 in the
[1:] SYSNAND CTRNAND if the safety test refuses to boot to HOME Menu.