$\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_2^{+}$ gives no ppt. $\Rightarrow$ no terminal triple bond but gives ppt. with $\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_2^{+}$ on treatment of $N{H}_2^{-}$

$\Rightarrow$ In the ring triple bond is not possible

• ${\mathrm{H}}_2/{\mathrm{Ni}}_2\mathrm{B}$ treatment reduces triple bond to double bond. Now possible options are 2, 3 and 4
• Oxidative ozonolysis gives non-resolvable compound. So only 4 is possible