Identify compound A from following reaction.

$$\mathrm{A}+\mathrm{C}_2 \mathrm{H}_5 \mathrm{MgBr} \xrightarrow[\text { ety }]{\text { drer }} \mathrm{B} \xrightarrow{\mathrm{H}_3 \mathrm{O}^{+}} \text {3-methylpentan-3-ol }$$

Identify product $$\mathrm{C}$$ in following conversion.

m - Hydroxy Benzaldehyde $$ \xrightarrow[\text { [Protection of }-\mathrm{OH} \text { group] }]{\mathrm{C}_6 \mathrm{H}_5 \mathrm{CH}_2 \mathrm{Cl}} $$ $$ \mathrm{A} \xrightarrow{[\mathrm{O}]} \mathrm{B} $$ $$ \xrightarrow[\text { [deprotection of }-\mathrm{OH} \text { group] }]{} $$ C

Identify the reagent used in following conversion.

Pent -3 -enenitrile $$\xrightarrow{\mathrm{A}}$$ pent -3 -enal

What is the product formed when side chain chlorination of toluene is carried out followed by acid hydrolysis at $$373 \mathrm{~K}$$ ?