How many molecules of methyl iodide are required to obtain tetramethyl ammonium iodide from dimethyl amine?

The conversion of $A$ to $B$ is an example of which reaction?
$\text{Propanenitrile}$ $\xrightarrow{LiAlH_4} A$ $\xrightarrow{CHCl_3 / \text{alcoholic } KOH, \Delta} B$

The main product of the following reaction will be:

In the given reaction,identify the reagent $A$:
$4-nitro-3-bromobenzenediazonium \ chloride \xrightarrow{A} 1-bromo-3-nitrobenzene$

Aniline in a set of the following reactions yielded a coloured product $Y$.
Aniline $\xrightarrow[(273-278 \ K)]{NaNO_{2}/HCl} X$ $\xrightarrow{N,N-dimethylaniline} Y$
The structure of $Y$ would be

The major product of the reaction is