Short answers, pulled from the story.
Dara Shikoh (1615-1659) was the eldest son of Mughal Emperor Shah Jahan and his designated heir-apparent. He is remembered as a scholar who argued for the shared mystical roots of Islam and Hinduism, and for losing the succession war to his younger brother, who became Emperor Aurangzeb.
Dara Shikoh completed two key works on this subject. Majma-ul-Bahrain ("The Confluence of the Two Seas"), written in 1654-55, explored mystical affinities between Sufism and Vedanta. He also translated fifty Upanishads from Sanskrit into Persian in 1657, calling the result Sirr-i-Akbar ("The Greatest Mystery"), and argued in its introduction that the Upanishads are the hidden book referenced in the Quran.
Dara Shikoh was executed on the 30th of August 1659 after losing the Mughal succession war to his brother Aurangzeb. A convocation of nobles and clergy declared him a threat to public peace and an apostate from Islam, and four of Aurangzeb's henchmen killed him in front of his son.
Dara Shikoh followed two principal spiritual teachers. He was introduced to Mian Mir, the Qadiri Sufi saint of Lahore, by Mullah Shah Badakhshi, Mian Mir's disciple and successor. Dara also became a follower of Sarmad Kashani, an Armenian Sufi-perennialist mystic.
Dara Shikoh was buried in Humayun's Tomb in Delhi after his execution in 1659. In 2020, engineer Sanjeev Kumar Singh concluded after four years of research that the grave lies under one of three cenotaphs in the northwestern chamber beneath the dome of the tomb, a finding supported by five of seven members of an Archaeological Survey of India expert committee.
In 2017, the New Delhi Municipal Council renamed Dalhousie Road in central Delhi to Dara Shikoh Road. A library he built in 1637 was later converted into India's second partition museum. Following the AMU Centenary Dara Shikoh Conference in December 2021, all written works by and about him became accessible through a dedicated digital library.