Was the prayer obligatory before the night of Al-Isra wal-Mi'raj, and did the Prophet (peace be upon him) perform it in its current form and number of rak'ahs, and when was it mandated in the form and times known today?

The five daily prayers were ordained on the night of the Isra' and Mi'raj, a year and a half before the Hijra. Originally, they were fifty prayers, then reduced to five. The Prophet (peace be upon him) learned their timings from Jibreel (Gabriel) on the morning after the night of Isra'. The number of rak'ahs (units) for the five daily prayers was two rak'ahs, then it was increased for residents after the Hijra, except for the Maghrib prayer.

The Prophet (peace be upon him) and his Companions used to pray before the five daily prayers were ordained. Some scholars are of the opinion that two rak'ahs were obligatory in the morning and two rak'ahs in the evening.