Azo dyes are organic compounds that contain an azo bond $(-N=N-)$

(1)

There is no azo bond $-N=N-$ formation in this case.

So, azo dye compound is not formed

(2)

Azo dye $(-N=N-$) is not formed in this reaction.

Benzonitrile reaction with H$_2$SO$_4$, gives benzoic acid product. $-CN$ becomes $-COOH$. Then, reaction with $PCl_5$ gives benzoyl chloride $(C_6H_5COCl)$. Its on reaction with aniline does not give $-N=N-$ type compound. So, azo dye compound is not formed.

(3)

Nitrobenzene on reaction with $\mathrm{Sn} / \mathrm{HCl}$ undergoes reduction reaction to form aniline. $-\mathrm{NO}_2$ is reduced to $-\mathrm{NH}_2$.

Aniline on reaction with $\mathrm{NaNO}_2 / \mathrm{HCl}$ undergoes diazotization reaction to form benzene diazonium chloride.

Nitrobenzene on reaction with So/HCl undergoes reduction reaction to form aniline. $-NO_2$ is reduced to $-NH_2$.

Aniline on reaction with $NaNO_2/HCl$ undergoes diazotization reaction to form benzene diazonium chloride.

$\mathrm{NaNO}_2+\mathrm{HCl} \longrightarrow \mathrm{NaCl}+\mathrm{HNO}_2$

Benzene diazonium chloride (Benzene diazonium salt) on reaction with $\beta$-naphthol and NaOH gives an azo compound.

Azo dye is formed in this reaction

(4)

Azo dye is not formed.