Which substance is responsible for the characteristic smell of mustard oil?

Which of the following compounds is expected to be the most basic?

Compare the basic strengths of the given compounds:

The following two reactions give the same foul-smelling product $Z$. $C_2H_5Cl \xrightarrow{X} Z$ and $C_2H_5CONH_2 \xrightarrow{Br_2, NaOH} Y \xrightarrow{CHCl_3/ethanolic KOH, \Delta} Z$. $X$ and $Z$,respectively,are:

What are $A, B$ and $C$ in the following reaction?
$Ar-N_2^+ BF_4^- \xrightarrow{NaNO_2, \Delta, Cu} A + B + C$

$Ph-C \equiv CH$ $\xrightarrow[Excess]{HCl} X$ $\xrightarrow{KOH (aq.)} Y$ $\xrightarrow{CH_3-CH_2-NH_2} Z,$
$Z$ is known as