In the given reaction,
$Ph-C \equiv C-CH_3 \xrightarrow{H^{+}/Hg^{2+}} A$
the product $A$ is

The reagents to carry out the following conversion are:

The major products $P$ and $Q$ in the following reactions,respectively,are:
$H_3C-C \equiv C-CH_2CH_3 \xrightarrow{H_2, \text{Lindlar's Catalyst}} P$
$H_3C-C \equiv C-CH_2CH_3 \xrightarrow{Na/\text{liquid } NH_3} Q$

The isomerisation of $1-$butyne to $2-$butyne can be achieved by treatment with

An unknown compound $(A)$ has a molecular formula $C_4H_6$. When $(A)$ is treated with excess of $Br_2$, a new substance $(B)$ with formula $C_4H_6Br_4$ is formed. $(A)$ forms a white precipitate with ammoniacal silver nitrate solution. $(A)$ may be:

In the reaction,$H_3C-C\equiv C-H$ $\xrightarrow[2. x]{1. NaNH_2, \Delta}$ $\xrightarrow{3. y} H_3C-CH=CH-CH_3$ (trans form),$x$ and $y$,respectively are