Which of the following complex is octahedral, diamagnetic and the most stable?

The correct order of electronegativity for given elements is:

The correct order of spin only magnetic moments for the following complex ions is

$$2 \mathrm{IO}_{3}^{-}+x \mathrm{I}^{-}+12 \mathrm{H}^{+} \rightarrow 6 \mathrm{I}_{2}+6 \mathrm{H}_{2} \mathrm{O}$$

What is the value of $$x$$ ?