Basically a partial downgrade/FrankenFirmware is when you get an error during the downgrade process using safesystemupdater. You can still get to the home menu but accessing the internet browser or system menu will cause the system to lock up.

1.Make sure you can start games, if you can't start games anymore your only options are this tutorial http://gbatemp.net/threads/guide-re...mware-w-o-upgrading-to-10-3-or-higher.413368/ or using system recovery to update to the latest official firmware, you lose all access to HB/CFW but at least your 3DS works like normal again

2.Find a game that comes with a higher firmware than your native firmware and at least higher than 9.2 (http://www.3dsdb.com/) The native firmware is the firmware you started the downgrade process from. I recommend either Bravely Second or the latest Fire Emblem. These come with 10.3 and I've heard that downgrading from 10.3 has a higher chance of success. These are both great games so if for some reason it does not work you have something to play when you system recover or to sell when it does, since they have a high resale value being recent releases.

If you started the downgrade process from 10.3 already you might be lucky and the partial downgrade might've gone far enough that the 3DS thinks it is actually on 9.2, this way any game above 9.2 will work

3.Start the game and you will get a prompt asking you to install an update, accept it and once it is done your 3DS will be back to normal and ready for another downgrade attempt.

 

[Logan Pockrus]

I would say, though, that if you can manage to access the Homebrew Launcher it may be advisable to try to use (safe)sysUpdater on your frankenfirmware to try to escape (I read that somewhere credible...right here on the 'temp).

It may be dangerous, so if you end up bricking your system doing this don't say I didn't warn you...but it shouldn't brick.