What is the order of basic strength for $CH_3NH_2$ and $(CH_3)_3N$ in an aqueous solution?

Which of the following substances turns blue litmus red?

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 correct decreasing order of the basic strength is

Choose the correct option.

Identify the compound that will react with Hinsberg's reagent to give a solid which dissolves in alkali.