The rate of $S_N1$ reaction will be faster for which of the following bromides?

Identify $A$ in the following reaction:

Dehydrohalogenation of an alkyl halide is a/an

Chlorination of toluene in the presence of light and heat followed by treatment with aqueous $NaOH$ gives:

Which among the following is $NOT$ a feature of $S_{N}2$ mechanism?

For the reactions given below:
$(I)$ Cyclohexyl chloride $\rightarrow$ Cyclohexyl cation + $Cl^-$,$\Delta H_1^{\circ}$
$(II)$ Cyclohex$-2-$enyl chloride $\rightarrow$ Cyclohex$-2-$enyl cation + $Cl^-$,$\Delta H_2^{\circ}$
$(III)$ Benzyl chloride $\rightarrow$ Benzyl cation + $Cl^-$,$\Delta H_3^{\circ}$
$(IV)$ Chlorobenzene $\rightarrow$ Phenyl cation + $Cl^-$,$\Delta H_4^{\circ}$
The correct decreasing order of enthalpies of reaction for producing the carbocation is: