Which one of the following reactions is not an example of a redox 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?

Which of the following occurs with $KMnO_4$ in neutral or faintly alkaline medium?

Which of the following options are correct for the reaction
$2[Au(CN)_2]_{(aq)}^{-} + Zn_{(s)} \rightarrow 2Au_{(s)} + [Zn(CN)_4]_{(aq)}^{2-}$
$A.$ Redox reaction
$B.$ Displacement reaction
$C.$ Decomposition reaction
$D.$ Combination reaction
Choose the correct answer from the options given below:

$A$ white crystalline salt $[A]$ reacts with dilute $HCl$ to produce a suffocating gas $[B]$ and also forms a yellow precipitate. When gas $[B]$ is passed through acidified potassium dichromate,it turns the solution green,forming $[C]$. Identify $A, B$,and $C$ respectively.

In order to oxidize a mixture of $1 \text{ mole}$ each of $FeC_2O_4$, $Fe_2(C_2O_4)_3$, $FeSO_4$, and $Fe_2(SO_4)_3$ in an acidic medium, the number of moles of $KMnO_4$ required is: