What is standard electrode potential?

Which statement is correct for $\Delta G$ and $E_{cell}$ for a cell reaction?

Based on the given standard electrode potentials,identify the metal that can be displaced from its salt solution by all other metals listed.
$E^o Zn^{2+}/Zn = -0.76 \ V, E^o Cu^{2+}/Cu = +0.34 \ V$
$E^o Ag^+/Ag = +0.80 \ V, E^o Co^{2+}/Co = -0.28 \ V$

Given the standard reduction potentials at $25\,^oC$ for the following half-reactions:
$Zn^{2+}_{(aq)} + 2e^- \rightleftharpoons Zn_{(s)}, E^o = -0.76\,V$
$Cr^{3+}_{(aq)} + 3e^- \rightleftharpoons Cr_{(s)}, E^o = -0.74\,V$
$2H^+_{(aq)} + 2e^- \rightleftharpoons H_{2(g)}, E^o = 0.00\,V$
$Fe^{3+}_{(aq)} + e^- \rightleftharpoons Fe^{2+}_{(aq)}, E^o = +0.77\,V$
Which of the following is the strongest reducing agent?

Identify the representation of the standard hydrogen electrode.

The standard reduction potentials for $Cu^{2+}|Cu$ and $Cu^{2+}|Cu^{+}$ are $0.337 \, V$ and $0.153 \, V$ respectively. What is the standard electrode potential for the $Cu^{+}|Cu$ half-cell in $V$?