In which of the following compounds, sulphur exhibits both positive and negative oxidation states?

In the reaction ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{Cr}}_2{\mathrm{O}}_7\to {\mathrm{N}}_2+4{\mathrm{H}}_2\mathrm{O}+{\mathrm{Cr}}_2{\mathrm{O}}_3$,

What is the number of electrons lost by each $\mathrm{N}$ atom?

In the half-reaction ${\mathrm{S}}_2{\mathrm{O}}_3^{-2}\rightleftharpoons {\mathrm{S}}_4{\mathrm{O}}_6^{-2}$, what is the number of electrons that must be added?

${\mathrm{Cu}}_2\mathrm{S}+{\mathrm{MnO}}_4^{-}\rightleftharpoons {\mathrm{Cu}}^{2+}+{\mathrm{SO}}_2+{\mathrm{Mn}}^{2+}$

How many electrons will be lost from $1$ mole of ${\mathrm{Cu}}_2\mathrm{S}$ in the above reaction?

${\mathrm{C}}_2{{\mathrm{O}}_4}^{2-}+{{\mathrm{MnO}}_4}^{-}\to {\mathrm{Mn}}^{2+}+{\mathrm{CO}}_2$

The above reaction takes place in