Here's a short story:

The Byzantine Empire, also referred to as the Eastern Roman Empire, was the continuation of the Roman Empire in the East during Late Antiquity and the Middle Ages, when its capital city was Constantinople (modern-day Istanbul, which had been founded as Byzantium). It survived the fragmentation and fall of the Western Roman Empire in the 5th century AD and continued to exist for an additional thousand years until it fell to the Ottoman Turks in 1453. During most of its existence, the empire was the most powerful economic, cultural, and military force in Europe. Both "Byzantine Empire" and "Eastern Roman Empire" are historiographical terms created after the end of the realm; its citizens continued to refer to their empire as the "Roman Empire" (, tr. ; ), or "Romania" (), and to themselves as "Romans". 

Several signal events from the 4th to 6th centuries mark the period of transition during which the Roman Empire's Greek East and Latin West divided. Constantine I (r. 324–337) reorganised the empire, made Constantinople the new capital, and legalised Christianity. Under Theodosius I (r. 379–395), Christianity became the Empire's official state religion and other religious practices were proscribed. Finally, under the reign of Heraclius (r. 610–641), the Empire's military and administration were restructured and adopted Greek for official use instead of Latin. Thus, although the Roman state continued and Roman state traditions were maintained, modern historians distinguish Byzantium from ancient Rome insofar as it was centred on Constantinople, oriented towards Greek rather than Latin culture, and characterised by Orthodox Christianity. (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: What is another name for the Byzantine Empire?
Guess: Eastern Roman Empire

Question: In the early days, what was its capital city called?
Guess: Constantinople

Question: What is it currently called?
Guess: Istanbul

Question: Founded by?
Guess: Byzantium

Question: When it was existing, was it the most powerful force?
Guess: Yes

Question: Where exactly?
Guess: Europe.

Question: What did the citizens called the empire?
Guess: "Roman Empire"

Question: and themselves?
Guess: "Romans".

Question: What happened from the 4 and 6th centuries?
Guess: Roman Empire's Greek East and Latin West divided

Question: Who reorganized the empire?
Guess: Constantine I

Question: and did he legalize Christianity?
Guess: yes

Question: and what was the new capital?
Guess: Constantinople

Question: Under whose reign, did Christianity become the official state religion?
Guess: Theodosius I n

Question: Was it the only religion that was practiced?
Guess: Yes

Now answer the following question in the same format.

Question: Under who reign was the administration restructured?

Heraclius