Which of the following is oxidised by $SO_2$?

Iron is dropped in dilute $HNO_3$,it gives:

In which of the following reactions, chlorine acts as an oxidising agent?
$(i)$ $CH_3CH_2OH + Cl_2 \longrightarrow CH_3CHO + HCl$
(ii) $CH_3CHO + Cl_2 \longrightarrow CCl_3CHO + HCl$
(iii) $CH_4 + Cl_2 \stackrel{hv}{\longrightarrow} CH_3Cl + HCl$
The correct answer is

$A$ solution of colourless salt $H$ on boiling with excess $NaOH$ produces a non-flammable gas. The gas evolution ceases after sometime. Upon addition of $Zn$ dust to the same solution,the gas evolution restarts. The colourless salt$(s)$ $H$ is (are):

$KMnO_4$ acts as an oxidizing agent in weak alkaline medium. When weak alkaline $KMnO_4$ is treated with $KI$,iodide ion is oxidized to $.........$

Whenever a reaction between an oxidising agent and a reducing agent is carried out,a compound of lower oxidation state is formed if the reducing agent is in excess and a compound of higher oxidation state is formed if the oxidising agent is in excess. Justify this statement giving three illustrations.