Assuming complete ionization, same moles of which of the following compounds will require the least amount of acidified $\mathrm{K}\mathrm{M}\mathrm{n}{\mathrm{O}}_4$ for complete oxidation?

For the redox reaction, ${\mathrm{MnO}}_4^{-}+{\mathrm{C}}_2{\mathrm{O}}_4^{2-}+{\mathrm{H}}^{+}⟶{\mathrm{Mn}}^{2+}+{\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}$

The correct coefficients of reactants in the balanced equation are:

In view of the signs of ${\mathrm{\Delta }}_{\mathrm{r}}\mathrm{G}°$ for the following reactions: 

${\mathrm{PbO}}_2+\mathrm{Pb}\to 2\mathrm{PbO}$, ${\mathrm{\Delta }}_{\mathrm{r}}\mathrm{G}°<0$

${\mathrm{SnO}}_2+\mathrm{Sn}\to 2\mathrm{SnO}$, ${\mathrm{\Delta }}_{\mathrm{r}}\mathrm{G}°>0$

which oxidation states are more characteristics for lead and tin?

Consider the following reaction: 

$x{\mathrm{MnO}}_4^{-}+y{C}_2{\mathrm{O}}_4^{2-}+z{H}^{+}\to x{\mathrm{Mn}}^{2+}+2y{\mathrm{CO}}_2+\frac{z}{2}{\mathrm{H}}_2\mathrm{O}$ 

The values of $x$, $y$ and z in the reaction are, respectively: