Thank you
If the buyer cancels the order before you ship it, it does not count against your account health or affect your performance metrics like the cancellation rate. Amazon expects that buyers can change their minds, and cancellations initiated by buyers are completely normal and won’t negatively impact you. However, if you as the seller cancel orders after accepting them because you’re out of stock or for other reasons, that would hurt your account health by increasing your seller-initiated cancellation rate, which Amazon monitors closely.
Nope.
No. As long as you get the buyer requested cancellation header.