Arrange the following compounds in order of decreasing rate of hydrolysis for $SN_1$ reaction:
$(I)$ $C_6H_5CH_2Br$
$(II)$ $p-CH_3-C_6H_4-CH_2Br$
$(III)$ $p-(CH_3)_2CH-C_6H_4-CH_2Br$
$(IV)$ $p-CH_3CH_2-C_6H_4-CH_2Br$

For the reaction:
$RCH_2Br + I^{-} \stackrel{\text{Acetone}}{\longrightarrow} RCH_2I + Br^{-}$
The correct statement is:

The insecticide containing $99\%$ $\gamma-isomer$ of benzene hexachloride is known as

For the given reaction,what is the major product '$A$'?
$3-\text{ethylbenzonitrile} + Br_2 \xrightarrow{UV \text{ light}} A$

Which of the following compounds will show retention in configuration on nucleophilic substitution by $OH^{-}$ ion?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$ : Haloalkanes react with $KCN$ to form alkyl cyanides as a main product while with $AgCN$ they form isocyanide as the main product.
Reason $(R)$ : $KCN$ and $AgCN$ both are highly ionic compounds.
In the light of the above statement,choose the most appropriate answer from the options given below: