Oxalic acid when treated with potassium permanganate in the presence of an acid,produces

Assign $A, B, C, D$ from the given type of reaction.
$ZnSO_4 \, (aq) + MgCl_2 \, (aq) \longrightarrow$ No reaction

$A$ solution of $KMnO_4$ on reduction yields either a colourless solution,a brown precipitate,or a green solution depending on the $pH$ of the solution. What different stages of the reduction do these represent and how are they carried out?

Potassium permanganate acts as an oxidant in neutral,alkaline,as well as acidic media. The final products obtained from it in the three conditions are,respectively:

$KMnO_4$ oxidises $S_2O_3^{2-}$ to $SO_4^{2-}$ in medium $x$ and $NO_2^-$ to $NO_3^-$ in medium $y$. $x$ and $y$ are respectively:

The colour of an iodine solution is discharged by shaking it with an aqueous solution of: