Although chlorobenzene does not undergo the Ullmann reaction,the presence of which group at the $o-$ and $p-$ positions of chlorobenzene makes it possible to undergo the Ullmann reaction?

The reaction shown below is an example of Nucleophilic Aromatic Substitution. Which of the following halides $(-X)$ is most readily replaced?

The following transformation proceeds through:

The correct order of melting point of dichlorobenzenes is

The set of compounds in which the reactivity of the halogen atom in ascending order is:

The reaction of compound $P$ with $CH_3MgBr$ (excess) in $(C_2H_5)_2O$ followed by addition of $H_2O$ gives $Q$. The compound $Q$ on treatment with $H_2SO_4$ at $0^{\circ}C$ gives $R$. The reaction of $R$ with $CH_3COCl$ in the presence of anhydrous $AlCl_3$ in $CH_2Cl_2$ followed by treatment with $H_2O$ produces compound $S$ [$Et$ in compound $P$ is ethyl group].
$(1)$ The product $S$ is
$(2)$ The reactions,$Q$ to $R$ and $R$ to $S$,are

$A$. Dehydration and Friedel-Crafts acylation	$B$. Aromatic sulfonation and Friedel-Crafts acylation
$C$. Friedel-Crafts alkylation,dehydration and Friedel-Crafts acylation	$D$. Friedel-Crafts alkylation and Friedel-Crafts acylation

Given the answer question $(1)$ and $(2)$