Can I submit my capstone project in my final project for certification test
Yes, the Capstone project can be submitted as the final project for certification test, but it should be uploaded on hackster.io first in your personal account. This link can then be used in the exam section.
However, it is highly recommended to create new projects using the Bolt IoT module as it will help in widening your concepts and help you to enhance your knowledge hereby using your creativity. So, surely try to build a project or two and upload them on hackster.io because hey, the certificate is just a formality but, the actual knowledge lies within your mind.