Which one of the following has the highest boiling point?

The reaction:
$CH_3CH_2I + KOH_{(aq)} \to CH_3CH_2OH + KI$
is classified as :

Identify the alkyl halide that undergoes $SN^2$ reaction most rapidly.

Arrange the following in order of $C-Br$ bond strength in a polar solvent. The structures are as follows:
$(I)$ $1$-methylcyclohexa-$2,4$-dienyl bromide
$(II)$ cyclohexa-$2,4$-dienyl bromide
$(III)$ $1$-methylcyclopenta-$2,4$-dienyl bromide
$(IV)$ cyclopenta-$2,4$-dienyl bromide

$CH_3Br + Nu^{-} \rightarrow CH_3-Nu + Br^{-}$
The decreasing order of the rate of the above reaction with nucleophiles $(Nu^{-})$ $A$ to $D$ is
$[Nu^{-} = (A) \, PhO^{-}, (B) \, AcO^{-}, (C) \, HO^{-}, (D) \, CH_3O^{-}]$

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