Alcohols combine with acetylene in the presence of mercury compounds as catalyst to form

Consider the following reaction sequence:
$C_6H_5-CH=CH-CHO$ $\xrightarrow[35^{\circ}C]{LiAlH_4} A$ $\xrightarrow[Excess]{CH_3MgBr} B$
Identify $B$ in the reaction.

Explain the dehydration reaction of $2$-methylbutan-$1$-ol with concentrated $H_2SO_4$.

What is the final product (major) $A$ in the given reaction?

What are $X$ and $Y$ in the following reaction? $R-OH + PCl_5 \rightarrow X + Y + HCl$

$n$-Propyl alcohol and isopropyl alcohol can be chemically distinguished by which of the following reagents?