well i am new to this since i cfw mine yesterday with b9s. just asking if its possible for him to change from ntrboot to b9s and see if he then can install cias
NTRboot is a method of hacking the 3DS system with custom firmware.
Try not to mistaken or confuse this for BootNTR, a type of loader that boots NTR custom firmware.
Boot9strap (B9S) is a signature hack you install on the 3DS internal NAND. This is the core component of what makes permanent or presistent custom firmware possible.
Luma3DS is the defacto or most popular entry custom firmware.
There are also Rei-Six, ReiNand, CakesFW, and NTR to name a few other custom firmwares.
Also, understand the 3DS firmware is a separate entity from custom firmware.
You can think of custom firmware more like add-ons to the 3DS operating system.