Before you submit
Every answer is graded together. An answer computed inside a wrong earlier file does not count, however well it was computed - so check each stage using its check endpoint before you move on.
Resubmitting is safe. Once an answer is recorded as correct, a later wrong submission will not undo it. Entries remain subject to organiser review and disqualification. Up to 30 submissions an hour.
The JSON is required. It is stored only if your answer is correct, it is never published, and the organisers read it to check entries and settle a close finish. It is deleted 28 days after the challenge closes. Your participant key is stripped out before it is stored.