$R-CH_2-CCl_2-R \xrightarrow{\text{Reagent}} R-C \equiv C-R$
The reagent is

The end product of the following sequence is
$CaC_2$ $\xrightarrow{H_2O} B$ $\xrightarrow[HgSO_4]{H_2O, H_2SO_4} C$

Acetylene can be obtained by the reaction:

The distinguishing test for a triple bond containing acidic hydrogen is:

What is the product when acetylene reacts with hypochlorous acid $(HOCl)$?

The relation between $(B)$ and $(C)$ is:
$CH_3-C \equiv CH$ $\xrightarrow{NaNH_2}$ $\xrightarrow{CH_3-I} (A)$ $\xrightarrow{Li/liq. NH_3} (B)$
$CH_3-C \equiv CH$ $\xrightarrow{NaNH_2}$ $\xrightarrow{CH_3-I} (A)$ $\xrightarrow[Pd/CaCO_3]{H_2} (C)$