Short answers, pulled from the story.
Emperor Constantine the Great officially dedicated his new capital on the 11th of May 330. This ceremony marked the official birth of Constantinople on the site of ancient Byzantium after he selected the location in 324.
Architects Anthemius of Tralles and Isidore of Miletus built the dome of Hagia Sophia between 532 and 537 under Emperor Justinian I. The cathedral cost twenty thousand pounds of gold to construct and replaced a previous basilica destroyed during the Nika riots of 532.
By the tenth century, the city housed between five hundred thousand and eight hundred thousand people. Foreigners numbered around sixty thousand out of four hundred thousand total residents by the late twelfth century.
Theodosius II built triple-wall fortifications rising eighteen meters high between 413 and 414 that remained unbreached until gunpowder arrived. Arab armies besieged the city twice from 674 to 678 and secondly from 717 to 718 but Greek fire destroyed their fleets.
The empire fell on the 29th of May 1453 when approximately thirty-three thousand people were captured by Ottoman troops. By May 1453 defenders numbered only four thousand seven hundred Greeks plus two hundred foreigners totaling under eight thousand men.
On the 28th of March 1930 the city was officially renamed Istanbul ending centuries of use for its former name. The Turkish Republic was proclaimed in 1923 moving the capital to Ankara while the city remained Turkey's largest commercial hub.