$KI$ is oxidised into $I_2$ by using the reagent

Which of the following reactions does not involve either oxidation or reduction?

Consider the reactions:
$2S_2O_3^{2-}(aq) + I_2(s) \to S_4O_6^{2-}(aq) + 2I^-(aq)$
$S_2O_3^{2-}(aq) + 2Br_2(l) + 5H_2O(l) \to 2SO_4^{2-}(aq) + 4Br^-(aq) + 10H^+(aq)$
Why does the same reductant,thiosulphate,react differently with iodine and bromine?

The reaction of $Na_2S_2O_3$ with iodine gives

Hot concentrated sulphuric acid is a moderately strong oxidizing agent. Which of the following reactions does not show oxidizing behaviour?

$20 \ mL$ of $Fe^{2+}$ solution of certain concentration has completely reacted with $20 \ mL$ of $0.01 \ M \ K_2Cr_2O_7$ in acidic medium. If $20 \ mL$ of same $Fe^{2+}$ solution has reacted completely with $20 \ mL$ of $KMnO_4$ solution in acidic medium,the molarity of $KMnO_4$ solution is: (in $M$)