$(ii)$ The $+ M$ effect of $- OCH _{3}$ group increases the basic strength of the following compound. $+ M$ effect of $- OCH _{3}$ is greater than $+ I$ effect of $- CH _{3}$

$(iii)$ Among the given options, the following compound is the most basic as the $- NH _{2}$ group does not involve in the resonance.

$(iv)$ Among the given options, the following compound is the least basic as - $NH _{2}$ group is involved in the resonance.

Thus, the correct order of basic strength is

$iii > ii > i > iv$