You don't have to take the course, you can apply straight for the certification on this page in the Academy. Just scroll down and expand the timezone and pick date you want to sign up for.

If you scroll even further down you can also see the requirements for the exam.

1. How can I register for Intermediate Developer exam? – Please find the link here to register https://academy.mendix.com/link/certifications/22/intermediate 
2. Is it compulsory to join the “2-day course” in order to attend the exam? – Not compulsory
3. How many days/weeks does the mendix platform need to schedule exams? – Schedules will be available. It is a virtual session. you can pick your slot based on your availability.