As said by both above, yes, the newer and more updated b9s is compatible with all firmwares, but the key part is it isn't free on firmwares above 11.3. For 11.4 and above, a compatible flashcart is required, which costs around 20 dollars. A second modded 3ds can work too, or soldering in a hardond, but both of those methods are arguably more expensive and complex.