Which of the following bonds makes a hydrocarbon most reactive?

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

Which of the following will be the final product when $C_2H_2$ reacts with $HCl$?

Two moles of $HBr$ are added to $CH_3-C \equiv CH$ in the presence of peroxide to give:

Acetylene reacts with dilute $H_2SO_4$ in the presence of $HgSO_4$ to produce .......

$CH_3-C \equiv CH \xrightarrow[(ii) H_2O_2/OH^{\Theta}]{(i) BH_3-THF} (P)$
$CH_3-C \equiv CH \xrightarrow[(ii) NaBH_4]{(i) Hg(OAc)_2/H_2O} (Q)$
Choose the correct option