Which of the following reactions exhibits the minimum standard reduction potential?

For the cell involving the following reaction: $Zn_{(s)} + Ni^{2+}_{(aq)} \longrightarrow Zn^{2+}_{(aq)} + Ni_{(s)}$. Given $E^{\circ}_{\text{cell}} = 0.5 \ V$. What is the standard Gibbs energy change of the cell reaction (in $kJ$)?

If standard reduction potential $(E^{\circ})$ of $(Mg^{2+}_{(aq)} \mid Mg_{(s)})$,$(Ag^{+}_{(aq)} \mid Ag_{(s)})$,$(Zn^{2+}_{(aq)} \mid Zn_{(s)})$ and $(Cu^{2+}_{(aq)} \mid Cu_{(s)})$ are $-2.37 \ V$,$+0.79 \ V$,$-0.76 \ V$ and $+0.34 \ V$ respectively. Which of the following reaction is spontaneous?

Calculate the $E^{\circ}_{cell}$ of the cell $Al | Al^{3+} || H^+ | H_{2(g)}, Pt$ given that $E^{\circ}_{Al^{3+}/Al} = -1.66 \ V$. (in $V$)

For the following cell reaction,$Ag | Ag^{+} | AgCl | Cl^{-} | Cl_2, Pt$
$\Delta G_f^{\circ}(AgCl) = -109 \ kJ/mol$
$\Delta G_f^{\circ}(Cl^{-}) = -129 \ kJ/mol$
$\Delta G_f^{\circ}(Ag^{+}) = 78 \ kJ/mol$
$E^{\circ}$ of the cell is

Given $:$
$(i) \, Cu^{2+} + 2e^- \rightarrow Cu \,, \, E^o = 0.337 \, V$
$(ii) \, Cu^{2+} + e^- \rightarrow Cu^{+} \,, \, E^o = 0.153 \, V$
Electrode potential,$E^o$ for the reaction,
$Cu^{+} + e^- \rightarrow Cu \,,$ will be $............$ $V$.