Hi Subhrajit Pagal,
Registration validity only given due date is May 31, you can able to take exam at any time within a month after from the date you applied.
Yes exam link is valid for 1 month . Within 1 month you have to complete the exam otherwise link will get expired
The coupon code is needed for registering for the exam. So, logically I would say that the time limit applies to the registration of the exam. Reasoning from that point of view, the time limit for the link to take the exam should be valid for a month after registration. Unfortunately, I am not sure if Mendix applied the same reasoning.
Sorry, it's not a clear answer, but I get your confusion!