Questions FAQ
From MoodleDocs
See How to let teachers share questions between courses
If I change a question in the question bank, will it be changed in all the quizzes it appears?
Yes. See Tim Hunt's forum post https://moodle.org/mod/forum/discuss.php?d=234011&parent=1016542#p1016558
Is there a question creation module for Moodle 2.x
Yes. See this forum thread. It is currently available for Moodle 2.7 from the author's Github.