Short answers, pulled from the story.
Muhammad Sultan Mirza was born in 1375 as the elder son of Jahangir Mirza and the Sufi princess Khanzada Begum. His father was Timur's favorite son and original heir, while his mother was a maternal granddaughter of Jani Beg, Khan of the Golden Horde.
Timur appointed Muhammad Sultan Mirza as governor of Tabriz in 1386 when he was ten years old. He later served as governor of Turan in 1399 and received command over the lands of the former Mongol Ilkhanate two years later.
Muhammad Sultan Mirza led the army centre during the Battle of the Kondurcha River in June 1391. He initially served in scouting parties before Timur granted him command of the army centre for the engagement.
Timur selected Muhammad Sultan Mirza as heir apparent based primarily on his birth and lineage rather than position or accomplishment. His father Jahangir was the only one of Timur's four sons born of a free wife, which elevated Muhammad Sultan's status above his cousins.
Muhammad Sultan Mirza led the main body of the army during the Battle of Ankara on the 20th of July 1402. The Ottoman forces were decisively defeated and Sultan Bayezid I was taken captive shortly after the battle.
Muhammad Sultan Mirza was dispatched to the Ottoman capital of Bursa to seize Bayezid's treasury but was beaten by the Ottoman prince Süleyman Çelebi. The Timurid army plundered the remaining treasures and subsequently torched the city.