Which of the following is aromatic?

Consider the following sequence of reactions. In $Z$,the number of $sp^3$ carbons is $a$ and $sp^2$ carbons is $b$. The value of $(a+b)$ is:
$CH_3CH_2CH_2CH_2Br$ $\xrightarrow[\text{dry ether}]{Na} X$ $\xrightarrow[\text{10-20 atm}]{\text{Cr}_2\text{O}_3 / 773 \text{ K}} Y$ $\xrightarrow[\text{anhy. AlCl}_3]{\text{CH}_3\text{COCl}} Z$

Total number of deactivating groups in aromatic electrophilic substitution reaction among the following is:
$-COOCH_3$,$-NHCOCH_3$,$-NHCH_3$,$-CN$,$-OCH_3$

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.

The decreasing order of the rate of electrophilic aromatic substitution is:

Which of the following compounds is most reactive toward electrophilic substitution reaction?