How many $\pi$-bonds are present in a naphthalene molecule?

$n$-Butylbenzene on oxidation with hot alkaline $KMnO_4$ gives

When a mixture of concentrated $HNO_3$ and $H_2SO_4$ reacts with benzene at $353 \, K$,what is the name of this reaction?

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

When benzene is heated with acetic anhydride in the presence of anhydrous aluminium chloride at $80 \ ^\circ C,$ the product formed is :

Which catalyst is used in the following reaction?