The best preparation for this exam is to follow the Become a Rapid Developer Learning Path. And the questions in the exam are pretty much same as the questions at end of each module in the learning path i.e., a short quiz at the end of each module. Make sure you are good at answering those quizzes and you will be able to pass the real exam. Another good thing is that you can re-take those quizzes as many times as you like to improve your knowledge.
Exam format is only MCQ’s same as in the quiz I have mentioned above. I guess there are total 50 MCQ’s in the exam.
Re-take of test will cost you again. For details, its better to contact directly at firstname.lastname@example.org