Which element forms the maximum number of stable oxides?

When a mixture of manganese dioxide,potassium hydroxide and potassium chlorate is fused,the product obtained is

Mention the type of compounds formed when small atoms like $H$,$C$ and $N$ get trapped inside the crystal lattice of transition metals. Also,give the physical and chemical characteristics of these compounds.

When $MnO_2$ is fused with $KOH$,a coloured compound is formed. The product and its colour are:

Among $Co^{3+}$,$Ti^{2+}$,$V^{2+}$ and $Cr^{2+}$ ions,one if used as a reagent cannot liberate $H_{2}$ from dilute mineral acid solution,its spin-only magnetic moment in gaseous state is $.....$ $B.M.$ (Nearest integer)

Provide the structures for:
$1.$ $MnO_4^{-}$
$2.$ $MnO_4^{2-}$