Ok, I think I understand your question. If you are asking how ntrboot works, it's actually using a recovery mode Nintendo placed into the bootrom. Nintendo setup a method that could access the hardware at the bootrom level and then allow them to use their own NTR (nds) cart in order to access the system and do their repairs. NTRboot basically exploits this bootrom recovery method and allows us to gain access to bootrom and of course install our own code such B9S, GM9, FB3DS, and Luma3DS, to name a few.