What is the product formed when a primary amine reacts with a ketone?

The reagent used for the protection of the amino group during the nitration of aniline is:

Account for the following:
$(i)$ $pK_{b}$ of aniline is more than that of methylamine.
$(ii)$ Ethylamine is soluble in water whereas aniline is not.
$(iii)$ Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
$(iv)$ Although amino group is $o-$ and $p-$ directing in aromatic electrophilic substitution reactions,aniline on nitration gives a substantial amount of $m$-nitroaniline.
$(v)$ Aniline does not undergo Friedel-Crafts reaction.
$(vi)$ Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
$(vii)$ Gabriel phthalimide synthesis is preferred for synthesising primary amines.

The sequence of reagents which convert $p-$methyl aniline to $p-$methyl benzoic acid are

The product $(A)$ is:

Reaction of nitrous acid with aliphatic primary amine in the cold gives