Actually, we can still complete that mission when we get to May, just like what happened this month when April's missions opened .. It allowed us to open March's missions and accompli* ..

That's the problem tho, as far as i know, we cannot get the points but only finish the missions .. Aside from that, Cat Quiz mission from March have this bug or visual error where it keeps counting even if you already completed it 3 times but doesn't reduce your completion times ..