I scanned my own bank's QR code (which I have saved in my gmail) with Amazon UPI...Then instantly sent the money back to the same bank from where AZ debited the money from, manually by bank's UPI service...And got 50 cashback...I do this quite often when they give cashbacks or sending money...
Go to any of your bank account's mobile app...Grab your payment receiving QR code from there...Most banks do provide an option to share the QR code...If you have that option, share that QR code to your own gmail account...After the QR code successully comes as an email to your gmail,open that email containing the QR code on any computer or your other mobile phone...Now go to your Amazon app & scan that QR code from your computer monitor/other mobile screen & complete the payment to get the cashback instantly...