Which of the following is(are) example$(s)$ of nucleophilic addition reaction in the case of acetylene?

Which of the following reagents is most suitable to distinguish compound $(3)$ from the others?
$(1) \ CH_3-C \equiv C-CH_3$
$(2) \ CH_3CH_2CH_2CH_3$
$(3) \ CH_3CH_2C \equiv CH$
$(4) \ CH_3CH=CH_2$

In the following reaction,compound $A$ is formed,which reacts with $B$ to give product $C$. Identify $A$ and $B$.

In the reaction sequence $CaC_2$ $\xrightarrow{H_2O} A$ $\xrightarrow[dil. H_2SO_4]{Hg^{+2}} B$ $\xrightarrow{Ni} H_2 C$,the product $C$ is:

Identify the alkyne in the following sequence of reactions:
Alkyne $\xrightarrow{\text{H}_2, \text{Lindlar's catalyst}} A$ $\xrightarrow{\text{Ozonolysis}} B \text{ (only)}$
Given that $B$ is obtained from $\text{CH}_2=\text{CH}_2$ via the Wacker process.

The synthesis of $3$-octyne is achieved by adding a mixture of sodium amide and an alkyne to a bromoalkane. What are these bromoalkane and alkyne?