- If you haven’t claimed the certificate yet, then you are fine. Just re-do the challenges and then submit your new projects. (Agreeing to the Academic Honesty Pledge should have been a step before claiming the certificate).
- If you’re talking about the challenges (rather than projects). There isn’t a way to reset all of them in a section.( You can reset your entire account from the settings page.) The plagiarism issue is only really a concern for the projects that you submit for your certificate though.
You’re fine. You don’t have to reset anything, but you can if you want to. Every section ends in projects and those are what is relevant for certifications. Just don’t copy other people’s work for the projects.