If you scroll down on the rapid developer exam page, you can see the prerequisites:
Have knowledge of the Mendix platform by completing the Become a Rapid Developer Learning Path or the Rapid Developer Classroom Course.
Laptop (system requirements can be found here)
It's also good to keep in mind that it's an open book exam with no time limit. You can make full use of the Mendix documentation, the modeler, the learning paths, etc, so if you're not sure, you can always spend some time to find the information you need.
The Rapid exam is pretty doable with only some study of one or two weeks including the academy course. So: go for it.
if i didn’t pass the exam in the first time
what will be happen?