Which hydrocarbon reacts with sodium in liquid ammonia?

Maximum bond energy of $C-H$ bonds is found in the compound:

Identify the products $A$ and $B$ in the following reaction sequence:
$Ph-CH(Br)-CH_2-Br$ $\xrightarrow[(ii) NaNH_2]{(i) alc. KOH} A$ $\xrightarrow{NaNH_2, CH_3CH_2-Cl} B$

Identify the structure of $M$ based on the following reaction scheme:

$CH_3COOH$ is reacted with $CH \equiv CH$ in the presence of $Hg^{2+}$,the product is:

At low temperatures,the slow addition of molecular bromine to $CH_2=CH-CH_2-C \equiv CH$ gives: