What is the ruling on the ablution (wudu') and prayer of one who forgot to ensure that water reached a fissure in his face during ablution, while not knowing if water reached it, and must he repeat the ablution and the prayer?

Water must reach the outer surface of the body and what is considered similar to it, such as a wound, if possible without harm. If the wound heals, this obligation is lifted. As for the inner part of an open wound, water must reach it if possible without harm. However, if the wound has a deep cavity in the flesh, it is not obligatory to go beyond what is visible of it. When the wound heals, the obligation to make water reach that spot is lifted. What the questioner mentioned about the strong presumption of water covering the entire body is sufficient, and there is no need to repeat the ablution. He should ignore obsessive doubts.