Short answers, pulled from the story.
Rafi ud-Darajat was born on the 1st of December 1699 and died on the 6th of June 1719. He ascended to the Mughal throne on the 18th of May 1719 and ruled for only three months and six days before his death.
The Sayyid brothers were Sayyid Hassan Ali Khan Barha and Sayyid Hussain Ali Khan Barha. They acted as kingmakers who deposed Farrukhsiyar and installed Rafi ud-Darajat as a puppet ruler to maintain their grip on the empire.
Rafi ud-Darajat granted the Marathas Chauth and Sardeshmukhi rights in six Mughal provinces. Chauth was a tax levied at 25 percent of the revenue while Sardeshmukhi was an additional 10 percent.
Nekusiyar declared himself emperor at Agra Fort on the 18th of May 1719 to challenge Rafi ud-Darajat. The Sayyid brothers retook Agra Fort within three months and confined Nekusiyar at the Salimgarh Fort until his death in 1723.
Rafi ud-Darajat's remains were interred near the shrine of the Sufi saint Khawaja Qutbuddin Bakhtiar Kaki at Mehrauli in Delhi. This location reflected the religious and cultural traditions of the Mughal elite.