A compound C7H9N gives an alkali-soluble product with benzenesulfonyl chloride, forms an orange dye when diazotised at 273 K and added to alkaline…

Alkali-soluble sulfonamide means a primary amine (Hinsberg test). Benzylamine is primary but its diazonium salt, being aliphatic, decomposes with $\mathrm{N_2}$ loss to the alcohol and cannot couple, so the dye test excludes it. Of the toluidines, only the para isomer has a symmetric 1,4-disubstituted ring, which gives the $\mathrm{AA'BB'}$ pattern of two doublets; the ortho and meta isomers show four distinct aromatic protons. Hence 4-methylaniline (p-toluidine).