Which of the following species acts as reducing agent during working of hydrogen-oxygen fuel cell?

Standard potential $\left(\mathrm{E}^{\circ}\right)$ of $\mathrm{Zn}_{(\mathrm{aq})}^{+2}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Zn}_{(\mathrm{s})}$ is -0.76 V .

What is standard potential of reaction $2 \mathrm{Zn}_{(\mathrm{s})} \longrightarrow 2 \mathrm{Zn}_{(\mathrm{aq})}^{+2}+4 \mathrm{e}^{-}$?

Which from following formulae is used to obtain value of $\mathrm{E}_{\text {cell }}^r$ for a reaction taking place in Dry cell?

For a Galvanic cell consisting zinc electrode and standard hydrogen electrode,

$$ \mathrm{E}^{\mathrm{o}}\left(\mathrm{Zn}_{(\mathrm{aq})}^{+2} \mid \mathrm{Zn}_{(\mathrm{s})}\right)=-0.76 \mathrm{~V} $$

Identify the reaction that takes place at positive electrode during working of cell?