Which from the following is the correct relationship between standard Gibbs energy change and standard cell potential?

Calculate the standard cell potential for the galvanic cell $Zn_{(s)} | Zn^{2+}_{(aq)} || Ag^{+}_{(aq)} | Ag_{(s)}$,given that $E^o_{Zn^{2+}/Zn} = -0.76 \ V$ and $E^o_{Ag^{+}/Ag} = +0.80 \ V$. (in $V$)

According to standard electrode potential,which is the strongest reducing agent and oxidising agent?
$Al (-1.66 \ V), Cu (+0.34 \ V), Li (-3.05 \ V), Ag (+0.80 \ V)$

In a cell,the following reactions take place:
$Fe^{2+} \rightarrow Fe^{3+} + e^{-}$ $\quad$ $E^{\circ}_{Fe^{3+} / Fe^{2+}} = 0.77 \, V$
$2I^{-} \rightarrow I_{2} + 2e^{-}$ $\quad$ $E^{\circ}_{I_{2} / I^{-}} = 0.54 \, V$
The standard electrode potential for the spontaneous reaction in the cell is $x \times 10^{-2} \, V$ at $298 \, K$. The value of $x$ is .... (Nearest Integer)

$MnO_4^- (aq) + 8H^+ (aq) + 5e^- \to Mn^{2+} (aq) + 4H_2O (l)$; $E_1^o = 1.51 \ V$
$MnO_2 (s) + 4H^+ (aq) + 2e^- \to Mn^{2+} (aq) + 2H_2O (l)$; $E_2^o = 1.21 \ V$
$MnO_4^- (aq) + 4H^+ (aq) + 3e^- \to MnO_2 (s) + 2H_2O (l)$; $E_3^o = ?$
Value of $E_3^o$ will be ............ $V$

If standard reduction potentials $(E^0)$ of $(Al^{+3}_{(aq)}|Al(s))$, $(Fe^{+2}_{(aq)}|Fe(s))$, $(Cu^{+2}_{(aq)}|Cu(s))$ and $(Ag^{+1}_{(aq)}|Ag(s))$ are $-1.66 \text{ V}$, $-0.44 \text{ V}$, $+0.34 \text{ V}$ and $+0.79 \text{ V}$ respectively, which of the following reactions is non-spontaneous?