In the following groups: $I. -OAc$,$II. -OMe$,$III. -OSO_2Me$,$IV. -OSO_2CF_3$. The order of leaving group ability is:

The major product of the following reaction is:

Differentiate between the $S_N2$ and $S_N1$ mechanisms of alkyl halides.

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

The correct reactivity order for $E_2$ reaction with alcoholic $KOH$ will be:
$(i)$ $3-$chlorocyclohexene derivative (conjugated system)
(ii) $1-$chlorodecalin derivative (with double bond)
(iii) $1-$chlorodecalin (saturated)

Identify $A$ and $B$ in the following sequence of reaction: