Can GraphQL be used for refunds on a merchant portal?

[RaymondN]

Hi, our team is making a payment app. However, we've got some questions about the refund and our hosted checkout page.

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Questions:

#1 We allow our merchants to refund on our Merchant Portal. Could we call GraphQL after a merchant refund on our portal? or the refund must be initiated on the Shopify admin?

#2 Do we have to notify Shopify if a customer leaves on our payment hosted checkout? The checkout page provides a one-hour time window for customers to complete payment. They can actually close the hosted checkout page or leave it there for one hour to expire the payment session.

#3 Regarding the questions above, what happens if the customer closes the checkout page and selects our payment service to proceed with the payment again?