that's not necessary, if you rename the update to "updateb.dat"you can leave it on the errorscreen for a couple of minutes and it is updated. (check the website for the update name though, i could be wrong about that).Firmware v1.25 supports DSi 1.45 and 3DS 8.1.0-19x
Last time 3DS changed their whitelist for DS Cards (0004800F484E4841) on FW 7.0.0-13
If you never used your DSTWO on actual FW, you might need to update itself
first on another DS/3DS that still accepts your Card.