Which of the following reactions do not involve oxidation reduction?

$\begin{array}{l}\mathrm{I}. 2\mathrm{Cs}+2{\mathrm{H}}_2\mathrm{O}⟶2\mathrm{CsOH}+{\mathrm{H}}_2\\ \mathrm{II}. 2{\mathrm{CuI}}_2⟶2\mathrm{CuI}+{\mathrm{I}}_2\\ {\mathrm{III}. \mathrm{NH}}_4\mathrm{Br}+\mathrm{KOH}⟶\mathrm{KBr}+{\mathrm{NH}}_3+{\mathrm{H}}_2\mathrm{O}\\ \mathrm{IV}. 4\mathrm{KCN}+\mathrm{Fe}(\mathrm{CN}{)}_2⟶{\mathrm{K}}_4\left[\mathrm{Fe}(\mathrm{CN}{)}_6\right]\end{array}$

I. $\left.\begin{array}{c}\mathrm{Cs}\to {\mathrm{Cs}}^{1+}+e^{-}\text{(Oxidation) }\\ {\mathrm{H}}_2\mathrm{O}+e^{-}⟶\stackrel{\odot }{\mathrm{O}}\mathrm{H}+\frac{1}{2}{\mathrm{H}}_2 (\mathrm{Reduction})\end{array}\right]$

Hence, redox reaction

 II. $$\begin{gathered} {\left.\begin{array}{c}{\text{e}}^{-}{\text{+Cu}}^{2+}\stackrel{ }{\to }{\text{Cu}}^{1+}\text{(Reduction)}\\ 2{\mathrm{I}}^{⊝}\underset{ }{\to }{\mathrm{I}}_2+2{\mathrm{e}}^{-}\left(\mathrm{Oxidation}\right)\end{array}\right]}_{ } \\ \mathrm{Hence}, \mathrm{redox} \mathrm{reaction}. \end{gathered}$$

III. $\begin{array}{c}\oplus \\ {\mathrm{NH}}_4\\ \mathrm{x}=-3\end{array}\stackrel{ }{\to }\begin{array}{c}{\mathrm{NH}}_3\\ \mathrm{x}=-3\end{array}(\mathrm{No} \mathrm{change} \mathrm{in} \mathrm{oxidation} \mathrm{number} ) \mathrm{Hence}, \mathrm{reaction} \mathrm{is} \mathrm{not} \mathrm{redox}$

IV. No change in the oxidation number of either ${\mathrm{Fe}}^{2+}$ or ${\mathrm{CN}}^{⊝}$ in both reactant and product; hence, not redox reaction