If you are doing the learner licence practice, then you do all of the questions every time you do the module - the point is that repeated exposure will ensure you learn it more effectively.
If you are taking a course as a trainee who has been invited by a manager, they will choose whether you only need to do the questions you got incorrect if you don't get 100% on a module. Here's how they choose if you see all questions or only the ones you got wrong.
If you purchased the course for yourself, you always have to do all the questions each time you take a module.
For unit standard courses, you only do the questions that you either haven't submitted answers for, or that have been marked as Not Yet Achieved (NYA).