I strongly advise against Preply. They employ basically all dark patterns possible. You pay for a "subscription" that can expire if the teacher needs to reschedule lessons. It's difficult to cancel. It really is a nightmare.
But that's not my goal. I'd like to be able to observe every grove, the physical encoding of data, and see if I could implement decoding from scratch. First problem is though that I don't know how to get a microscopic image of the disc.
This inspired me to read up on the low-level details of CD structure. I'm curious if anybody scanned an entire CD and shared the results, so that we could work with a raw image of disc that contains all its quirks, as opposed to the typical .iso format?