Can I submit Design which is created on HTML Template purchased from Themeforest

I have purchased an HTML template from Envato (Themeforest) and created an Examination Management System (PHP Script) on the frontend purchased from Envato so can I submit it on Codecanyon or I need my own HTML Design for it?

No, you would need permission/agreement from the original author

You need written permission by email from the author (who may want a single payment, share of profits etc.)

They will have to submit a ticket to suport and provide the ticket ID to you to include with your submission

More info here:

You will have to take written permission from the original author of the theme.