If I recall correctly, this was lost when the site software upgraded.
If it's possible to bring the challenge quizzes back, I'm sure that the Site Development Team will do so.
JP is correct. The upgrade caused the EF Challenge Quiz software to become inoperative, so in anticipation of such a probability, we have safety stored all the quiz questions in a Hellmann's mayonnaise jar on my back porch until such time we can get a suitable, new quiz program which will work with the current site software.
Unfortunately, the records of those who have taken the quizzes in the past are inaccessible. When we get a new quiz back, we will have to start from the git go.