In which of the following is the $C-Cl$ bond length minimum?

$C_6H_5NH_2$ $\xrightarrow[\substack{NaNO_2 \\ HCl, 0-5^{\circ}C}]{} X$ $\xrightarrow[CuCl]{HCl} Y$ $\xrightarrow[\text{dry ether}]{CH_3Cl, Na} Z$
What is $Z$ in the sequence of reactions?

Which of the following compounds undergoes electrophilic substitution slower than benzene?

The reaction of benzene diazonium chloride with $Cu$ powder and $HCl$ is known as:

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 $(2)$

Which of the following gives only one monosubstituted product upon further electrophilic substitution?