$CH_3 - C \equiv C - CH_3 \xrightarrow[CH_3COOH]{BH_3, THF} \text{Major product}$

In its reaction with silver nitrate,acetylene shows:

Which of the following has the shortest $C-C$ bond length?

In the given reaction $x$ is:
$CH_3 - C \equiv CH$ $\xrightarrow{Excess\ HCl} (A)$ $\xrightarrow{H_2O/OH^{-}} (x)$

$But-1-yne$ reacts with cold alkaline $KMnO_4$ to produce:

Consider the following sequence,where $A$ can be:
$A$ $(C_{3}H_{6}Cl_{2})$ $\xrightarrow[2. \, H^{+} \, (mild)]{1. \, \text{alcoholic } KOH / \Delta, \text{ followed by } NaNH_{2} / \Delta}$ $B$ $\xrightarrow[H_{2}O_{2} / OH^{-}]{B_{2}H_{6}}$ $C$
$A$ $\xrightarrow{aq. \, KOH \, (excess)}$ $C$
Identify $A$.