What is $X$ in the given reaction? $HC \equiv CH + 2AgNO_3 \xrightarrow{NH_4OH} X + 2NH_4NO_3 + 2H_2O$

The incorrect statement regarding ethyne is

Acetylene shows ........... in its reaction with silver nitrate.

Which of the following will be the final product when $C_2H_2$ reacts with $HCl$?

Identify the structure of the final product $(D)$ in the following sequence of reactions:
$Ph-CO-CH_3$ $\xrightarrow{PCl_5, \Delta} A$ $\xrightarrow{3 \text{ eq. } NaNH_2/NH_3} B$ $\xrightarrow{\text{Acidify}} C$ $\xrightarrow{1. B_2H_6, 2. H_2O_2/OH^-} D$
Total number of $sp^2$ hybridised carbon atoms in product $D$ is:

The reaction $R-C \equiv C-R \xrightarrow{H_2 / \text{Lindlar's catalyst}}$ gives the major product as ..............