I saw it but I thought someone had already given the answer.
With a firmware above 9.2 (such as yours in 9.9), you can't do anything other than playing homebrews or use a Sky3DS to play roms (much more limited of course).
You can't install CIAs and you can't downgrade.
There's only two ways to downgrade:
a) software downgrade (9.2 or below)
b) with a backup of the NAND while it had exploitable firmware and a hardmod
Both of those options can't be used in your case.
Someone did give an answer, I just wanted to double check with you since you had seemed more knowledgeable, plus wanted to confirm with multiple people.
But yeah looks like I'm out of luck in that case