If you cancel from the order page where it says you can still cancel, then no it won't be charged. If it ships and you then try to cancel, it won't cancel and it will be charged to you until you return it and get a refund.
No, Amazon doesn't charge you until the item is ready for shipment.
If you completed the order, payment would typically be charged immediately, you need to check on it because refunds occasionally get messed up.
nno
