The higher oxidation for $\mathrm{d}$$-$block elements is generally most stable with which halogen?

Which of the following reactions are disproportionation reactions?

$\left(\mathrm{i}\right)$ ${\mathrm{Cu}}^{+}⟶{\mathrm{Cu}}^{2+}+\mathrm{Cu}$
$\left(\mathrm{ii}\right)$ $3{\mathrm{MnO}}_4^{-}+4{\mathrm{H}}^{+}⟶2{\mathrm{MnO}}_4^{-}+{\mathrm{MnO}}_2+2{\mathrm{H}}_2\mathrm{O}$
$\left(\mathrm{iii}\right)$ $2{\mathrm{KMnO}}_4⟶{\mathrm{K}}_2{\mathrm{MnO}}_4+{\mathrm{MnO}}_2+{\mathrm{O}}_2$
$\left(\mathrm{iv}\right)$ $2{\mathrm{MnO}}_4^{-}+3{\mathrm{Mn}}^{2+}+2{\mathrm{H}}_2\mathrm{O}⟶5{\mathrm{MnO}}_2+4{\mathrm{H}}^{+}$

Select the correct statement(s) regarding oxides of transition metals.