Is it guaranteed that a person's prayer for the righteousness of their religion and worldly life will be answered if they are sincere in their supplication?

The Muslim worships Allah through supplication, certain of its answer, taking the necessary means, then relying upon Allah, for Allah knows best what benefits His servant. And he does not despair, even if the wait is long; for supplication is an intended act of worship. It has been authentically reported from the Prophet, peace and blessings be upon him, that if a Muslim supplicates with a supplication that contains no sin or severing of family ties, Allah grants him one of three things: either his supplication is hastened for him, or it is stored for him in the Hereafter, or an equivalent amount of evil is averted from him. So, every supplicant is answered, but the answer varies: sometimes it occurs exactly as supplicated, and sometimes it is replaced with something else. Persistence, good opinion of Allah, and not despairing are among the greatest means of obtaining an answer.