(i) The deflection in the magnetic compass shows that the current is flowing in the circuit.
(ii) The bulb did not glow because the current passing through the circuit could be weak to make it glow. Also, it may happen because of other reasons like bulb may be fused or the connections may be loose.
(iii) Increase in the number of turns in the coil wound around the magnetic compass would increase the magnetic field around the magnetic compass which will result in the increase in the deflection in the magnetic compass.
(iv) Increase in the number of cells will further increase the deflection of the magnetic compass.