Short answers, pulled from the story.
Malik Ahmad declared independence on the 28th of May 1490. He established a de facto independent sultanate in the northwestern Deccan region immediately following this declaration.
The Ahmadnagar Sultanate was founded by Malik Ahmad, whose family were the Kulkarnis of Pathri. His ancestors had migrated to the Vijayanagara Empire due to religious persecution or famine before he became governor of Beed.
Sultan Hussain Nizam Shah I joined an alliance with Bijapur, Bidar, and Golconda to attack Rama Raya at Talikota in late January 1565. The battle resulted in the beheading of Rama Raya by Sultan Nizam Hussain himself, marking a decisive defeat for the Vijayanagara Empire.
The Ahmadnagar Sultanate existed as an independent kingdom from 1490 until 1636. Aurangzeb defeated Shahaji in 1636, which marked the end of independent rule for the Nizam Shahi dynasty.
Malik Ambar introduced a revenue system based on models used in Northern India and Gujarat that classified lands according to fertility levels. He abolished revenue farming and allowed cultivators to pay cash equivalent to approximately one-third of the yield after initially paying two-fifths in kind.