Does the submission need to be made at the time of registration? Is it possible to get information on the uploading method of submission material before the actual submission?

You can register once, and then go back and enter as many submissions as you want later—up until the final deadline. You may also register, enter a placeholder design (a fake), make payment—and upload finalized work later. This could secure a lower priced fee or dated coupon rate, like the Earlybird discount, even if your work is not quite finished. However, all finalized materials must be received by the Late Deadline.