$HC\equiv CH + 2HOCl \rightarrow A$. What is the product $A$?

Which of the following reactions forms an aldehyde as a product?

Given below are two statements:
Statement $I$: One mole of propyne reacts with excess of sodium to liberate half a mole of $H_2$ gas.
Statement $II$: Four $g$ of propyne reacts with $NaNH_2$ to liberate $NH_3$ gas which occupies $224 \ mL$ at $STP$.
In the light of the above statements,choose the most appropriate answer from the options given below:

What is the end product of the following sequence of operations?
$CaC_2$ $\xrightarrow{H_2O} A$ $\xrightarrow[Hg^{2+}]{dil. H_2SO_4} B$ $\xrightarrow[H_2]{Ni} C$

Which of the following gases,when passed through a warm dilute solution of $H_2SO_4$ in the presence of $HgSO_4$,gives acetaldehyde?

Explain the acidic nature of ethyne.