1) Edit the quiz and set the retakes to 9999, this will set it to unlimited.
2) Well this is not available but you can do the pagination in the unit, then in per page you can show one question.
3) Please refer the video tutorial I shared above, you can see the explanation is shown in the practice quiz, refer:
http://prntscr.com/cls0a4, when you click on explanation it will show you the explanation.
4) Similarly to the 3rd point the explanation and check answer is shown in the practice quiz.
PS: If you use some third party plugins for this then it may conflict with wplms quizzes.