I assume the best way is to contact support to get definite answers. I’m just some random user, so this is just what I know and it could all be wrong (although then it would become a serious ethical issue so it’s probably true enough).
Mapillary does not store unblurred photos. After a short grace period, the original is deleted. You can never get it back from Mapillary.
Here’s a relevant–if old–reply: Anonymize (blurring faces and license plates) before upload - #10 by eneerhut
You can see who took the photo but actually having profile information, like contact information, is up to the person. It’s unlikely you can directly contact most people. And, from experience, no one is likely to keep too many old photos/videos around - they take up literal terabytes of space. I would be very surprised if anyone has photos from a year ago.