Which of the following metals cannot displace $H_2$ from acids or $H_2O$ from its compounds?

The standard electrode potentials of $Zn^{2+}/Zn$ and $Ag^{+}/Ag$ are $-0.763 \ V$ and $+0.799 \ V$ respectively. The standard potential of the cell is ............ $V$.

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

The $E^{0}_{Red}$ values of $A, B, C,$ and $D$ are $0.8 \, V, 0.79 \, V, 0.34 \, V,$ and $-2.37 \, V$ respectively. Which element can displace the other three from their salt solutions?

What is the oxidation and reduction potential of standard hydrogen electrode?

Consider the following relations for $EMF$ of an electrochemical cell:
$(i)$ $EMF$ of cell = (Oxidation potential of anode) $-$ (Reduction potential of cathode)
$(ii)$ $EMF$ of cell = (Oxidation potential of anode) $+$ (Reduction potential of cathode)
$(iii)$ $EMF$ of cell = (Reduction potential of anode) $+$ (Reduction potential of cathode)
$(iv)$ $EMF$ of cell = (Oxidation potential of anode) $-$ (Oxidation potential of cathode)
Which of the above relations are correct?