How many $\pi$ electrons are present in naphthalene to decide its aromaticity?

Among the following statements on the nitration of aromatic compounds,the false one is:

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:

Give the reaction for the acylation of benzene and its mechanism.

Most common reactions of benzene (aromatic hydrocarbon) and its derivatives are

Assertion : Benzene exhibits two different bond lengths, due to $C-C$ single and $C=C$ double bonds.
Reason : Actual structure of benzene is a hybrid of the following two structures.