How can I access the all the submissions ever placed on JOTFORM?

Is there a way i can access early submissions and delete them to free up space?

Yes, you can view all your submissions. Here's a guide on how to view your submissions.

https://www.jotform.com/help/269-How-to-View-Form-Submissions

And here's how to delete submissions.
https://www.jotform.com/help/377-How-to-Delete-Form-Submission-Data

Hope that helps. Let me know if you have any other concerns.