Does performing the Fajr prayer in Muzdalifah while retaining urine affect the validity of the Hajj or the prayer, knowing that an attempt was made to find a restroom without success due to the crowd?

There is no sin upon you, and your Hajj is valid, for warding off the two impurities (urine and feces) is not among the pillars or conditions of Hajj. Similarly, prayer, according to the majority of scholars, is considered disliked based on the Prophet's (peace and blessings be upon him) saying, "There is no prayer in the presence of food, nor when one is warding off the two impurities." What is negated here is the perfection of the prayer, not its validity. The Malikis, however, believe that severe urinary retention that prevents devotion invalidates the prayer.