Choose the correct option$(s)$ for the following set of reactions:

$C_3H_7I$ $(P)$ $\xrightarrow[\text{alc. } KOH]{\Delta}$ $Q$ $\xrightarrow{NBS}$ $R$ $\xrightarrow{KCN}$ $CH_2 = CH - CH_2 - CN$. $P$ can be:

Which one of the following compounds will be most reactive for $S_N1$ reactions?

How many isomers are possible for the compound with the molecular formula $C_2BrClFI$?

Given below are two statements:
Statement $I$: Due to increase in van der Waals forces, the order of boiling points is $CH_3CH_2CH_2I > CH_3CH_2I > CH_3I$.
Statement $II$: As $para$-dichlorobenzene is more symmetric, its melting point is higher than $ortho$-dichlorobenzene, however its boiling point is lower than $ortho$-dichlorobenzene.
In the light of the above statements, choose the correct answer from the options given below:

Product $A$ is