The reaction of toluene with chlorine in the presence of light gives

In the reaction,the major product formed is:

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.

In Friedel-Crafts alkylation,besides $AlCl_3$ the other reactants are

The Birch reduction of benzoic acid gives:

Hydrogenation of naphthalene $(P)$ with excess hydrogen gas stops cleanly at $1, 2, 3, 4-$ tetrahydronaphthalene $(Q).$ What conclusion can be drawn from this experiment?