Identify product $A$ in the following reaction:
$4-methylcyclohexyl bromide + OH^- \xrightarrow{S_N2} A$

The order of reactivity of the following alkyl bromides towards $S_N1$ reactions is:
$a$) $(CH_3)_2CHBr$
$b$) $CH_3CH_2Br$
$c$) $(CH_3)_3CBr$

The major product formed when $1$-Bromo-$3$-chlorocyclobutane reacts with metallic sodium in dry ether is

Match the reactions in List-$I$ with the features of their products in List-$II$ and choose the correct option.
| List-$I$ | List-$II$ |
| :--- | :--- |
| $(P)$ $(-)-1$-Bromo-$2$-ethylpentane $\xrightarrow{aq. NaOH, S_N2}$ | $(1)$ Inversion of configuration |
| $(Q)$ $(-)-2$-Bromopentane $\xrightarrow{aq. NaOH, S_N2}$ | $(2)$ Retention of configuration |
| $(R)$ $(-)-3$-Bromo-$3$-methylhexane $\xrightarrow{aq. NaOH, S_N1}$ | $(3)$ Mixture of enantiomers |
| $(S)$ $(3S, 5S)-5$-bromo-$3$-methylheptane $\xrightarrow{aq. NaOH, S_N1}$ | $(4)$ Mixture of structural isomers |
| | $(5)$ Mixture of diastereomers |

What is formed when toluene reacts with chlorine in the presence of light?

The following reaction,$(CH_3)_3CBr + H_2O \rightarrow (CH_3)_3COH + HBr$,is an example of: