14-day return period from Apple, no reason needed.
With Amazon, can only be returned if unopened unless it is damaged (at least, according to their policy; although you can take a chance that they will be kinder than their policy).
Interesting. They accepted my M1 MBP for a refund after I told them I have been using it. I sent it back, but have not gotten the money yet, so maybe I will hold off opening my M2 14" I bought from them and got today.