Why is the 3rd compound more basic than 2nd? This question is w.r.t the uploaded pic

It is because in 3rd option lone pair of nitrogen is not involved in aromaticity and resonance of Benzene ring and after the lone pair spended the compound has much stability but in 2nd option although lone pair are available,ring will be no longer stable after reaction

It is quite simple. In the II compound the ring contain 3 double bond. Atom N has lone pair electron(lpe) which it use to form a bond dounble bond. So the double bond will resonate simultaniously and it gives more stability to the N atom or you xan say that the lpe will not be release easily. Whereas in compound III there is no double bond in the ring so O atom has no chance to form a double bond using its lpe the O is more suseptable to relesing the lpe. Thus, it has more basic nature. .Good wishes.