Regarding your question about "Sundar," there is no widely known historical figure named Sundar who was killed alongside Bhagat Singh or Batukeshwar Dutt. Bhagat Singh was executed along with his comrades Sukhdev Thapar and Shivaram Rajguru.

Bhagat Singh and Batukeshwar Dutt were involved in significant acts of protest against British rule in India:

• Bhagat Singh was executed (hanged) by the British colonial government on March 23, 1931, in Lahore. He, along with Sukhdev and Rajguru, was convicted in the Lahore Conspiracy Case. The primary charges leading to his death sentence were:
  • The assassination of British police officer John P. Saunders in December 1928. This act was carried out in retaliation for the death of Lala Lajpat Rai, who succumbed to injuries sustained during a police lathi-charge.
  • The bombing of the Central Legislative Assembly in Delhi on April 8, 1929. This act was intended as a protest to "make the deaf hear" and not to cause casualties.
• Batukeshwar Dutt was not killed. He was arrested along with Bhagat Singh after the Central Legislative Assembly bombing in April 1929. While Bhagat Singh, Sukhdev, and Rajguru were sentenced to death for the Saunders murder, Batukeshwar Dutt was sentenced to transportation for life for his role in the Assembly bombing case. He suffered from tuberculosis during his imprisonment and was eventually released in 1937. He passed away in 1965.

Their actions and trials galvanized the Indian independence movement and cemented their status as iconic revolutionaries.