Match the reactant in Column-$I$ with the reaction in Column-$II$:

Column-$I$	Column-$II$
$(i)$ Acetic acid	$(a)$ Stephen
$(ii)$ Sodium phenate	$(b)$ Friedel-Crafts
$(iii)$ Methyl cyanide	$(c)$ $HVZ$
$(iv)$ Toluene	$(d)$ Kolbe's

Choose the correct option$(s)$ for the following reaction sequence. Consider $Q$,$R$ and $S$ as major products.

Give plausible explanation for each of the following:
$(i)$ Cyclohexanone forms cyanohydrin in good yield but $2,2,6-$trimethylcyclohexanone does not.
$(ii)$ There are two $-NH_2$ groups in semicarbazide. However,only one is involved in the formation of semicarbazones.
$(iii)$ During the preparation of esters from a carboxylic acid and an alcohol in the presence of an acid catalyst,the water or the ester should be removed as soon as it is formed.

Given below are two statements:
Statement $I:$ Ethyl pent$-4-$yn$-$oate on reaction with $CH_{3}MgBr$ gives a $3^{\circ}$ alcohol.
Statement $II:$ In this reaction,one mole of ethyl pent$-4-$yn$-$oate utilizes two moles of $CH_{3}MgBr$.
In the light of the above statements,choose the most appropriate answer from the options given below:

Compound $A$ was treated with a large excess of $CH_3MgBr$. The resulting product was exposed to $POCl_3$ /pyridine to give compound $B$,as one of many products.
Which of the following compounds can be $A$ ?

Saponification (basic hydrolysis) of $C_6H_5-CO-^{18}OCH_3$ will yield. [$^{18}O$ = mass $-18$ isotope of oxygen]