Hello,

Every degree will have a time limitation as per the university academic regulations. Most of the university doesn't allow a gap of more than 3-4 years. As per you case it is not possible to appear in the final year and resume your course after this huge gap of 18 years. You can contact your college regarding this issue but, it is likely to assume that there isn't any way to again appear for the final year.

Hope it helps!

Good luck!