You can now cancel an order when it is in packed/shipped status, as long as the cancel option is available on App/Website/M-site. This includes items purchased on sale also. Any amount paid will be credited into the same payment mode using which the payment was made

Yes, You can modify the shipping address of your order before we have processed (packed) it, by updating it under 'change address' option which is available under ‘My order’ section of App/Website/M-site

If you had selected Cash on Delivery, there is no amount to be refunded because you haven't paid for your order. For payments made via Credit Card, Debit Card, Net Banking, or Wallet you will receive refund into the source account within 7-10 days from the time of order cancellation. If payment was made by redeeming PhonePe wallet balance then, then refund will be instant post order cancellation, which can be later transferred into your bank account, by contacting PhonePe customer support team.