Which of the following compounds reacts with $KCN$ to form a cyanide?

An alkyl halide may be converted into an alcohol by

When chloroform is exposed to air and sunlight,it gives

Among the following chlorides, the compounds which will be hydrolysed most easily and most slowly in aqueous $NaOH$ solution are respectively:
$1$. Methoxymethyl chloride $(CH_3OCH_2Cl)$
$2$. Benzyl chloride $(C_6H_5CH_2Cl)$
$3$. Neopentyl chloride $((CH_3)_3CCH_2Cl)$
$4$. Propyl chloride $(CH_3CH_2CH_2Cl)$

Non-occurrence of the following reaction
$Br^{-} + CH_3OH \rightarrow BrCH_3 + OH^{-}$,is due to

Increasing the concentration of an electrophile (substrate) in a typical $S_N2$ reaction by a factor of $3$ and the concentration of the nucleophile by a factor of $3$ will change the reaction rate to