Number of acidic hydrogen atoms in $but-1-yne$ are

$HC \equiv CNa + Cl - CH_2 - CH_2 - CH_2 - I \to (A)$; Major product $(A)$ is

The general formula of an alkyne is:

$A$ gas decolourises bromine in $CCl_4$ and forms a precipitate with ammoniacal silver nitrate. The gas is

When propyne is passed through a red hot iron tube at $873 \ K$,the reaction gives a product having the molecular formula of:

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