Short answers, pulled from the story.
Asaf-ud-Daula was the Nawab wazir of Oudh, ratified by the Mughal emperor Shah Alam II, who ruled from the 26th of January 1775 until his death on the 21st of September 1797. He was the son of Shuja-ud-Daula and became Nawab at age 26 following his father's death.
Asaf-ud-Daula built the Bara Imambara as a relief project during the famine of 1784, when even the nobles of Awadh had been reduced to penury. He employed over 20,000 workers on the structure, including commoners and noblemen, providing wages and food to those who had none.
During the construction of the Bara Imambara, common laborers built the structure by day. On the night of every fourth day, the nobles and upper-class people were employed in secret to demolish what had been built, receiving payment for that work so that their need for charity would remain hidden.
The proverb is "Jisko na de Maula, usko de Asaf-ud-Daula," which translates to "to whom even God does not give, Asaf-ud-Daula gives." It originated during his lifetime and is still repeated in Lucknow today.
Asaf-ud-Daula assumed power on the death of his father Shuja-ud-Daula on the 28th of January 1775, with the support of the British East India Company. British Colonel John Parker defeated a mutiny led by Asaf's younger brother Saadat Ali, securing the succession.
The Rumi Darwaza is a gateway standing sixty feet tall in Lucknow, built in 1784 under Asaf-ud-Daula. It was modeled after the Sublime Porte, known as Bab-i Humayun, in Istanbul, and is considered one of the notable examples of exchange between Ottoman and Nawabi architecture.