Is it Islamically permissible to intentionally delay the two rak'ahs of Fajr (the Sunnah prayer before the obligatory Fajr prayer) until after the Fajr prayer without an excuse, or is that forbidden? And is it permissible to delay them for a minor excuse, such as being occupied with supplication or reviewing what the imam will recite?

A Muslim should not neglect performing the Sunnah prayers at their prescribed times according to the Sharia, except when there is a valid excuse, because performing an act of worship at its appointed time is better than making it up later. The two rak'ahs of Fajr are among the supererogatory prayers that the Prophet, peace and blessings be upon him, consistently performed. Aisha, may Allah be pleased with her, said: "The Prophet, peace and blessings be upon him, was never more diligent in observing any supererogatory prayer than he was concerning the two rak'ahs before Fajr." The Prophet, peace and blessings be upon him, also said: "The two rak'ahs of Fajr are better than the world and what is in it." If a Muslim misses performing them at their appointed time, there is no sin upon him, but he has missed out on much good, and it is legislated to make them up after the obligatory prayer.