This issue only needs to be tested in 1 device. Create 2 quizzed with "Close the quiz" date enabled and set to a past date. In one of the quizzes add 1 question, leave the other without questions. In the app, login as teacher and open the quiz without question. Check that you see a message in red saying that the quiz doesn't have any question. Check that there's no Preview button. Now open the quiz that has at least 1 question. Check that you see a warning (yellow color) saying that the quiz is not available. Check that you see a Preview button and you can use it to preview the quiz. Now open the closed quiz with 1 question but using a student account. Check that the quiz not available message is displayed in red.