$2-$Butyne reacts with $Na$ in liquid $NH_3$ to form:

Identify the major product $A$ in the following reaction sequence:
$CH_3-CH=CH-CH_3$ $\xrightarrow[CCl_4]{Br_2}$ $\xrightarrow[(ii) NaNH_2]{(i) alc. KOH} (A)$

In which reaction is the final product $Ph-C \equiv CH$?

$CH_3-C \equiv CH \xrightarrow[dil. H_2SO_4]{HgSO_4} (A)$
$CH_3-C \equiv CH \xrightarrow[(1) BH_3.THF]{(2) H_2O_2/HO^{-}} (B)$
Products $(A)$ and $(B)$ can be differentiated by:

Consider the following reaction sequences and choose the correct option:
$L \xrightarrow{Na/liq. NH_3} Ph-C \equiv C-Me \xrightarrow[Lindlar's \ Catalyst]{H_2, Pd/C} K$
$L \xrightarrow{HBr, \text{benzoyl peroxide}} N$
$K \xrightarrow{HBr} M$

What is Lindlar's catalyst?