Which of the following compounds has the lower boiling point?

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

Which of the following rules applies in the reaction:
$CH_3CHBrCH_2CH_3 \xrightarrow{alc. KOH}$
$(i)$ $CH_3CH = CHCH_3$ (major product)
$(ii)$ $CH_2 = CHCH_2CH_3$ (minor product)

Explain the concept of retention of configuration in a chemical reaction with an example.

What is the correct decreasing order of the relative rate of solvolysis for the following alkyl halides in formic acid containing a small amount of water?
$(I) \ CH_2=CH-CH_2Cl$
$(II) \ CH_2=CH-CH(CH_3)Cl$
$(III) \ CH_2=C(CH_3)CH_2Cl$
$(IV) \ CH_3CH=CH-CH_2Cl$

The major product of the above reaction is: