Which reaction is $NOT$ a redox reaction?

$20 \, mL$ of $0.02 \, M \, K_2Cr_2O_7$ solution is used for the titration of $10 \, mL$ of $Fe^{2+}$ solution in the acidic medium. The molarity of $Fe^{2+}$ solution is ........... $\times 10^{-2} \, M$ (Nearest Integer).

$(NH_4)_2Cr_2O_7$ (Ammonium dichromate) is used in fireworks. The green coloured powder blown in air is

$15 \ mL$ of aqueous solution of $Fe^{2+}$ in acidic medium completely reacted with $20 \ mL$ of $0.03 \ M$ aqueous $Cr_{2}O_{7}^{2-}$. The molarity of the $Fe^{2+}$ solution is ........... $\times 10^{-2} \ M$ (Round off to the Nearest Integer).

$KMnO_4$ reacts with oxalic acid according to the equation:
$2MnO_4^- + 5C_2O_4^{2-} + 16H^+ \to 2Mn^{2+} + 10CO_2 + 8H_2O$
Here $20 \ mL$ of $0.1 \ M \ KMnO_4$ is equivalent to:

$40 \text{ mL}$ of $x \text{ M } KMnO_4$ solution is required to react completely with $200 \text{ mL}$ of $0.02 \text{ M}$ oxalic acid solution in acidic medium. The value of $x$ is: