a
Given $|\operatorname{adj}(\operatorname{adj}(\operatorname{adj} . A ))|=12^4$
$\Rightarrow| A |^{(n-1)^3}=12^4$
Given $n =3$
$\Rightarrow| A |^8=12^4$
$\Rightarrow| A |^2=12$
$| A |=2 \sqrt{3}$
We are asked
$\left| A ^{-1} \cdot \operatorname{adj} A \right|$
$=\left| A ^{-1}\right| \cdot|\operatorname{adj} A |$
$=\frac{1}{| A |} \cdot| A |^{3-1}$
$=| A |=2 \sqrt{3}$