The Ain-i-Akbari is a historical document that provides valuable insights into the Mughal Empire. It was written by Abu`l Fazl, a minister in the court of Emperor Akbar. The document is a part of a larger work called Akbar Nama, which is a detailed account of Akbar`s reign.

Option 1 is correct as Abu`l Fazl is the author of the Ain-i-Akbari.

Option 2 is correct as the Ain-i-Akbari is indeed a part of the Akbar Nama.

Option 3 is correct as the Ain-i-Akbari describes the Mughal Empire as having a diverse population and a composite culture. It provides information about the social, economic, and administrative systems of the empire, including details about the ruling classes, land revenue administration, and the cultural practices of different communities.

Option 4 is incorrect. There is no evidence to suggest that the Ain-i-Akbari was revised by Sadullah Khan on the orders of Shah Jahan.

In conclusion, the correct answer is option 4, as it provides incorrect information about the revision of the Ain-i-Akbari.