How many electrons $(e^-)$ are gained by the oxidizing agent $KMnO_4$ to convert into $MnO_4^{2-}$,$MnO_2$,$Mn_2O_3$,and $Mn^{2+}$ respectively?

Assign $A, B, C, D$ for the given type of reaction:
$Mn(NO_3)_2 + 2NaOH \longrightarrow Mn(OH)_2 \downarrow + 2NaNO_3$

Which of the following ions decolorizes acidic $KMnO_4$ solution?

Which of the following is a true statement?

$A$ 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?

Upon the addition of a solution $A$ to a strongly acidified solution of barium nitrate,a white precipitate was obtained which did not dissolve even after large addition of water. Solution $A$ contained