Should the person with urinary incontinence, who finds enough time for part of the prayer, pray it at the beginning of its time, or should he pray the prayer from which he caught a single unit (rak'ah)?

It is not prescribed to pray Asr before Dhuhr, due to the obligation of observing the proper sequence between the two present prayers and the two combined prayers according to many scholars. This issue does not fall under the ruling of the permissibility of neglecting the sequence if doing so would lead to missing the present prayer. If the time expires before one finishes the second prayer, it becomes void if the person has urinary incontinence and their ablution is nullified by the expiry of the time, and they must make up the prayer.