Check their annual report.

https://www.apple.com/environment/pdf/Apple_Environmental_Pr...

To see previous ones, simply change the year in the URL.

You can get to that from apple.com/environment or apple.com/2030 (which redirects to the former). Near the end, right before and in the appendix you can find third-party independent reviews and assessments.

Now, are those trustworthy? I don’t know. But it gives you the context to start looking. The broader document will also probably help answer the other specific questions.