Short answers, pulled from the story.
Nizam-ul-Mulk Asaf Jah I, born Mir Qamar-ud-din Khan on the 11th of August 1671, was the founder of the Asaf Jahi dynasty and the first Nizam of Hyderabad. He established autonomous rule over the Deccan on the 11th of October 1724, creating what became one of the largest and most prosperous princely states of the British Raj, covering 95,337 square miles at its height.
After serving as Grand Vizier of the Mughal Empire from 1722 to 1724, Nizam-ul-Mulk clashed with Emperor Muhammad Shah's court faction and was ordered transferred to Awadh. He refused, resigned his post, and marched south to the Deccan, defeating the Emperor's appointed governor Mubariz Khan at the Battle of Shakar Kheda in 1724. Muhammad Shah was forced to recognise him as permanent Viceroy of the Deccan, and later that year Nizam proclaimed himself ruler and founded the Asaf Jahi dynasty.
When Nader Shah ordered a massacre of Delhi's population after nine hundred of his soldiers were killed in a bazaar brawl, neither Emperor Muhammad Shah nor any of his ministers dared approach the Persian ruler. Nizam-ul-Mulk stepped forward alone and persuaded Nader Shah to end the killing. Nader Shah ended the massacre on condition and withdrew to Persia.
From 1719 to 1722, Nizam-ul-Mulk organized Central Asian nobles in the Mughal court against the Sayyid brothers. He defeated their military forces near Burhanpur in June 1720 and again in July 1720. Sayyid Hussain Ali Khan was assassinated on the 9th of October 1720 by a Turkic soldier from among Nizam's sympathisers, and his brother Sayyid Hassan Ali Khan Barha was poisoned in 1722. As reward, Muhammad Shah appointed Nizam as Grand Vizier.
Nizam-ul-Mulk dictated a seventeen-clause testament in Burhanpur shortly before his death on the 1st of June 1748. The document advised his successors on keeping troops well-fed, warned against declaring war unnecessarily, reminded them to remain subservient to the Mughal Emperor, and instructed his sons not to listen to slanderers or allow riffraff into their presence. He also included an apology for neglecting his wife.
His death in 1748 triggered immediate civil war among his sons and grandson, with Nasir Jung (1748-1750), Muzaffar Jang (1750-1751), and Salabat Jung (1751-1762) each contending for power, backed by European colonial forces and rival states. Stability only returned with the accession of Asaf Jah II, who reigned from 1762 to 1803 and signed the Treaty of Masulipatam in 1768, surrendering the coastal region to the East India Company.