How to fetch store credit balance of a customer?

With the new Store Credit Preview APIs, we can credit and debit the store credits for a customer. But how do you fetch a customer profile’s current store credit balance?

How do I know when the store credit balance is updated? Is there going to be a webook in the future?

Check out the Shopify webhook reference doc. They list various webhooks, so you might find an event that notifies you when a credit card is updated?