I would like to know if it's possible to pay my app users using FB Credits?
My idea is to buy FB Credits using my app account then when an user completes a task I will pay/transfer FB Credits to him. Is it possible?
It's possible but only available to a small number of companies as the minimum order value is very high (not sure exactly what is is)
You may be able to get more information by contacting the credits team at https://www.facebook.com/help/contact_us.php?id=204456519570236 but i'm not sure what the requirements are for access to those APIs