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

Give chemical reactions for the following conversions:
$1$. $2-$bromobutane from $2-$butyne
$2$. $2-$propanol and $1-$propanol from propyne

In the reaction sequence:
$CH_3-C\equiv CH$ $\xrightarrow{CH_3MgBr}$ $CH_4 + (A)$ $\xrightarrow[ (ii) H_2O/H^{\oplus} ]{(i) CO_2}$ $(B)$
$(B)$ will be:

In the reaction $x + H_2O \xrightarrow[H_2SO_4]{HgSO_4} CH_3-CO-CH_2-CH_3$,the reactant $x$ is:

Which of the following compounds on hydration (addition of $H_2O$) with $H_2SO_4/HgSO_4/H_2O$ gives an aldehyde as the major product?

$X$ (Symmetrical alkyne) $\xrightarrow{Hg^{2+}/H_3O^{+}}$ $2-$butanone. Which compound reacts with $Ag$ powder to give $X$?