The ii-V progression should be a half cadence rather than imperfect. I think it would also be helpful if you accepted "diminished seven" and "diminished 7" (or even "dim 7"), and "Picardy third" and "Picardy 3rd".
Yes, picardy 3rd should be accepted. Your definition of tritone is vague. I did appreciate your quiz and surprised I've not found it before. I have 25 quizzes on classical music online. Perhaps if you renamed it with "classical music" as a heading it would get more attention?
The ii-V progression should be a half cadence rather than imperfect. I think it would also be helpful if you accepted "diminished seven" and "diminished 7" (or even "dim 7"), and "Picardy third" and "Picardy 3rd".