Which of the following is the strongest reducing agent?

The electrode potentials are given as follows:
$Fe_{(aq)}^{3+} + e^- \to Fe_{(aq)}^{2+}$; $E^o = 0.771 \, V$
$I_{2(s)} + 2e^- \to 2I_{(aq)}^-$; $E^o = 0.536 \, V$
For the cell reaction $2Fe_{(aq)}^{3+} + 2I_{(aq)}^- \to 2Fe_{(aq)}^{2+} + I_{2(s)}$,the value of $E^o_{cell}$ is:

For the half-cell $Zn^{2+} | Zn$,the standard electrode potential $E^{\circ}$ is $-0.76 \ V$. What is the $e.m.f.$ of the cell $Zn_{(s)} | Zn^{2+}_{(aq)} (1 \ M) || 2H^{+}_{(aq)} (1 \ M) | H_{2(g)} (1 \ atm)$ in $V$?

The standard electrode potential of the cell $H_2 | H^{+} || Ag^{+} | Ag$ is .......... $V$.

The reaction is spontaneous if the cell potential is

On the basis of the following electrode potentials,which one is the strongest reducing agent?
$E^0_{Cr_2O_7^{2-}/Cr^{3+}} = 1.33 \text{ V}$,$E^0_{MnO_4^-/Mn^{2+}} = 1.51 \text{ V}$,$E^0_{Br_2/Br^{-}} = 1.09 \text{ V}$,$E^0_{Zn^{2+}/Zn} = -0.76 \text{ V}$