Which is/are correct about fuel cells?

Iodine $\left({\mathrm{I}}_2\right)$ and bromine $\left({\mathrm{Br}}_2\right)$ are added to a solution containing iodide $\left({\mathrm{I}}^{-}\right)$ and bromide $\left({\mathrm{Br}}^{-}\right)$ ions. What is the reaction occurred if the concentration of each species is $1 \mathrm{M}$?

The electrode potentials for the reactions are ${{\mathrm{E}}^{°}}_{{\mathrm{I}}_2/{\mathrm{I}}^{-}}=0.54 \mathrm{V}$ and ${\mathrm{E}}_{{\mathrm{Br}}_2/{\mathrm{Br}}^{-}}^{°}=1.08 \mathrm{V}$, respectively.

$\mathrm{MgO}$, $\mathrm{CuO}$ and ${\mathrm{Na}}_2\mathrm{O}$

Which of these oxides are reduced by hydrogen?

Which of the following oxides will decompose on heating?

$\mathrm{ZnO}, \mathrm{CuO}, \mathrm{MgO}$ and ${\mathrm{Ag}}_2\mathrm{O}$