Which alkyl halide has the highest bond enthalpy of the $C-X$ bond?

Considering the above reactions,the compound $A$ and compound $B$ respectively are:

$C_6H_{13}Br + OH^{-} \to C_6H_{13}OH + Br^{-}$ is an example of

The products $A$ and $B$ in the following reactions,respectively,are:
$A \xleftarrow{AgNO_2} CH_3-CH_2-CH_2-Br \xrightarrow{AgCN} B$

Arrange the following compounds in decreasing order of the rate of electrophilic addition reaction:
$(P)$ $p$-vinylbenzaldehyde
$(Q)$ $p$-vinylanisole
$(R)$ $p$-methylstyrene
$(S)$ $p$-dimethylaminostyrene

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