Should Fajr be prayed first, then Subh, or vice versa? And is it permissible to offer one before or after the other?

One must observe prayers at their prescribed times. The time for Fajr (dawn) prayer extends from the emergence of the second dawn (true dawn) until sunrise. Whoever intentionally delays it until its time expires has committed a major sin. However, one who misses it due to sleep or forgetfulness is excused and must pray it immediately upon remembering it. The Fajr prayer consists of two rak'ahs, preceded by two rak'ahs of Sunnah (definition) prayer (Sunnat al-Fajr/al-Subh/al-Raghibah). Whoever wakes up after sunrise should first pray the Sunnah and then the obligatory prayer, following the example of the Prophet (peace be upon him). Al-Fajr and Al-Subh are two names for the same prayer.