Is every supplication answered for whoever sincerely says, "There is no god but You; glory be to You, indeed I have been of the wrongdoers," and is that added to his good deeds if it is not answered for him?

The supplication of Dhul-Nun: (There is no deity except You; exalted are You. Indeed, I have been of the wrongdoers). No Muslim has ever supplicated with it for anything but Allah has responded to him. However, the answering of supplication depends on the fulfillment of conditions and the absence of impediments. When the conditions for answering are met and its impediments are removed, then Allah Almighty answers either swiftly in this world, or deferred to the Hereafter; by granting the supplicant good deeds in return for his supplication, or by averting evil from him equivalent to his supplication; as the Prophet, peace and blessings be upon him, said: "No Muslim supplicates with a supplication in which there is no sin or severing of ties of kinship, but Allah gives him one of three things: either He hastens his supplication for him, or He stores it for him in the Hereafter, or He averts from him evil equivalent to it."