I don't know much about updating with a Sky3DS, but with your firmware I don't think you need it.
Grab the most recent rxtools from
https://lavanoid.github.io/ and run it (read the readme for proper sd card setup/exploit preperation). Put the oldest TMD/APP files from the FBI injection folder on the SD card's root, too. Also, put sysupdater.cia on your root. You'll also need the 9.2U update pack from the site related to "3DS" and "ISO" files. (You can find it on google). It should be a .zip containing a whole folder of .cia files, which you should put in "SD:/update/<cia files here>"
Once you exploit, hold L and boot into the rxtools menu. Inject FBI into your SysNAND, then run rxtools pasta mode. In pasta mode, run FBI, install sysupdater, then perform the system update inside of sysupdater. Power off and you should reboot back into 9.2U.