Benzene vapour mixed with air when passed over $V_2O_5$ catalyst at $775 \ K$ gives

The correct order of reactivity of $(I)$ Aniline,$(II)$ Benzene,and $(III)$ Nitrobenzene towards electrophilic substitution reaction is .....

Which order is correct for the decreasing reactivity toward ring monobromination of the following compounds:
$I. \, C_6H_5CH_3$
$II. \, C_6H_5COOH$
$III. \, C_6H_6$
$IV. \, C_6H_5NO_2$

The number of $\pi$ electrons in the following molecule is:

Identify the product $X$ obtained in the following reaction:
$CH_{3}-(CH_{2})_{4}-CH_{3} \xrightarrow{Cr_{2}O_{3}, 773 \ K, 10-20 \ atm} X$

In the below mentioned compounds,the decreasing order of reactivity towards electrophilic substitution is: