For the acidic reaction $\mathrm{Cr}{}_2\mathrm{O}{}_7{}^{2-}+\mathrm{SO}{}_3{}^{2-}+\mathrm{H}{}^{+}\to \mathrm{Cr}{}^{3+}+\mathrm{SO}{}_4{}^{2-}+\mathrm{H}{}_2\mathrm{O}$ balanced with smallest whole numbers, select ALL correct statements.

1. A3 mol of $\mathrm{SO}{}_3{}^{2-}$ are oxidised per mol of $\mathrm{Cr}{}_2\mathrm{O}{}_7{}^{2-}$
2. B8 mol of $\mathrm{H}{}^{+}$ are consumed per mol of $\mathrm{Cr}{}_2\mathrm{O}{}_7{}^{2-}$
3. C$\mathrm{Cr}{}_2\mathrm{O}{}_7{}^{2-}$ acts as the reducing agent
4. D4 mol of $\mathrm{H}{}_2\mathrm{O}$ are formed per mol of $\mathrm{Cr}{}_2\mathrm{O}{}_7{}^{2-}$