Are there items (such as additional content, offers or currency) for sale that are used in the gameplay of your product?

Yes

Can your product be used without making any in-app purchases?

Yes

Are in-app purchases refundable?

Refund is not possible. However, you can contact the company [email protected]
only for game goods that have not been consumed within 7 days of purchasing the paid service.

What payment platform is used to facilitate these purchases? Do you use Epic Games’ platform or a 3rd-party (including your own) payment system?

It's only an Epic Games' platform.