Addition of $HCN$ to ethyne in the presence of $Ba(CN)_2$ as a catalyst gives:

The products of the reaction $CH_3 - C \equiv C - CH_2CH_3 \xrightarrow[(ii) \text{ Hydrolysis}]{(i) O_3}$ are .....

Complete the following reactions:
$(1)$ $CH \equiv CH + 2H_2 \xrightarrow[523-573 \ K]{Ni} ?$
$(2)$ $CH_3-C \equiv CH + 2H_2 \xrightarrow[or \ Ni, \Delta]{Pd \ or \ Pt} ?$

Write the following reaction:
$1$. Ozonolysis of ethyne.

Predict the product of the following reaction sequence:
$HC \equiv CH$ $\xrightarrow[\begin{smallmatrix} (2) \text{ excess } I-CH_2-(CH_2)_2-CH_3 \\ (3) \text{ } H^{\oplus} \end{smallmatrix}]{(1) \text{ excess } NaNH_2}$

Give a brief description of the structure of ethyne (acetylene).