What is the relationship between dreams and destiny, and do dreams come true when they are recounted without interpretation, or must they be interpreted in order to occur? And does a person's destiny change when a dream is mentioned, as opposed to not mentioning it?

Visions and dreams fall under divine decree (qadar), but a person's dream about something does not change anything from Allah Almighty's decree; what Allah has decreed will happen. A truthful vision might come to pass if it is interpreted, but the seer's not mentioning the vision and its not being interpreted does not avert anything from Allah's decree.