title key verification isn't a thing. title key is an additional layer of encryption for digital contents, you either have the correct title key in the ticket or you don't. it can't just be bypassed
cartridges don't do title key encryption, because cartridges don't have tickets. instead there is a different kind of (universal) game card encryption, several different kinds of keys contained in bootrom depending on if it's an older or newer game, and new 3ds-exclusive cartridges use different keys too. the way it works is a little complicated but in layman's term the key slot(s) we care about is write-only, and before the bootrom was dumped, we couldnt know what the keys actually were. you could ask the console to read and decrypt a 3ds rom, and we could still use the keys to decrypt, but without knowing what the actual key was (so we couldnt do decryption on pc without first generating xorpads on console)
you underestimate how strong the cartridge verifications are on the 3ds, if signatures were the only barrier then they would be no barrier at all... considering that making perfect signed copies of a cartridge rom is trivial, all you would need to do is put that same data on a bootleg chip and... that hasn't happened, because it's a lot more complicated than just passing signature checks. bootlegs can easily pass signature checks because it would be very easy to just use a signed rom. there's a reason why sky3ds had problems with antipiracy btw
my mistake though, I was thinking you actually knew what you were talking about and could help me figure it out
digital is different than physical, sort of. both are essentially just ncch containers, but cia also includes a ticket and a tmd (ncch metadata) where cartridges don't. they are encrypted differently but that doesnt really make a difference
cci is .3ds, it means nothing but a made up extension for familiarity because nobody would know what a .cci is otherwise. cxi is ncch, which is contents, which for game executables generally contains an exefs and romfs, among other things