The byzantine empire finally fell in 1453 to the persians indians turks greeks

It fell to the Turks. Most specifically to the Ottoman turks.

The turks began to advance through the Anatolian Peninsula since the 11th century. A decisive battle was the battle of Mazinkert in 1701 which debilitated the byzantine power in Anatolia.

With time, the turks  conquered other places not only in Anatolia, but also in Greece, reducing the Byzantine Empire to its capital, Constantinople, which finally fell in 1453 as stated in the question.

hello,

i'm not so sure but i hope this in anyway.

the president of russia is head of state, and of a multi-party system with executive power exercised by the government, headed by the prime minister, who is appointed by the president with the parliament's approval.

hope this : )

monasticism. people often do monasticism in monasteries