Which one of the following has the highest boiling point?

Benzyl bromide on reaction with magnesium in the presence of dry ether gives $'X'$. $'X'$ on reaction with ethanol gives $'Y'$. Then the compound $Y$ is

By passing excess $Cl_{2(g)}$ in boiling toluene, which one of the following compounds is exclusively formed?

The reaction of $3$-bromocyclohexene with $HBr$ yields $P_1$ and $P_2$ as major dibromo products. What is the relationship between $P_1$ and $P_2$?

The following reaction is supposed to take place through the $S_N1$ mechanism: $CH_3-C(Ph)(OH)-CH_2-CH_3 \xrightarrow{HI} \text{products}$. If the configuration of the substrate is $D$,then the configuration of the products will be:

Consider the following bromides.
The correct order of $S_N1$ reactivity is