Which of the following compounds has the lowest bond dissociation energy for a $C-H$ bond?

The products $P$ and $Q$ in the following sequence of reactions are:
$p$-Methylanisole $\xrightarrow{Li, EtOH, NH_3(l)} P$ $\xrightarrow[(ii) -78^{\circ}C, Me_2S]{(i) O_3 (1 \text{ equiv.})} Q$

The reaction is given as:
Naphthalene + Oxalyl chloride $\xrightarrow{AlCl_3} [X]$ $\xrightarrow{Na-Hg, HCl \text{ (excess)}} [Y]$
Product $Y$ is:

Match the following reactions in List-$I$ with their corresponding products in List-$II$:
List-$I$ (Reaction):
$A$. $\text{Benzene} + Cl_2 \xrightarrow{AlCl_3}$
$B$. $\text{Benzene} + CH_3Cl \xrightarrow{\text{anhyd. } AlCl_3}$
$C$. $\text{Benzene} + R-CO-Cl \xrightarrow{\text{anhyd. } AlCl_3}$
$D$. $\text{Toluene} \xrightarrow{(i) KMnO_4/KOH, (ii) H_3O^+}$
List-$II$ (Product):
$I$. $\text{Benzoic acid}$
$II$. $\text{Alkyl phenyl ketone}$
$III$. $\text{Chlorobenzene}$
$IV$. $\text{Toluene}$

Given the following structures:
$(I)$ $1,3,5-$trimethylbenzene (mesitylene)
$(II)$ $1,3-$dimethyl$-5-$methylenecyclohexa$-1,3-$diene
$(III)$ $1,3,5-$trimethylenecyclohexane
The enthalpy of hydrogenation of these compounds will be in the order as:

The total number of possible isomeric trimethyl benzene is