Short answers, pulled from the story.
John Howard, 1st Duke of Norfolk (c. 1425-1485), also known as Jack of Norfolk, was an English nobleman, soldier, and politician who was a close friend and loyal supporter of King Richard III. He was the first Howard to hold the dukedom of Norfolk and was created Duke of Norfolk on the 28th of June 1483. He was killed at the Battle of Bosworth Field on the 22nd of August 1485.
Howard commanded the vanguard of Richard III's army at Bosworth Field and was killed during the battle on the 22nd of August 1485. According to the Ballad of Lady Bessy, he was slain in single combat by the knight Sir John Savage. An alternative account holds that a Lancastrian arrow struck him in the face after his helmet's face guard had been torn off in an earlier clash with the Earl of Oxford.
Yes. Howard was the great-grandfather of Anne Boleyn, Henry VIII's second queen, and of Catherine Howard, Henry's fifth queen. His son Thomas Howard, 2nd Duke of Norfolk, had a daughter named Elizabeth Howard who married Sir Thomas Boleyn, 1st Earl of Wiltshire. Through Anne Boleyn, John Howard was also the great-great-grandfather of Queen Elizabeth I.
Howard was created Duke of Norfolk on the 28th of June 1483 because he was the hereditary heir to the dukedom through his Mowbray descent on his mother's side, and because his alliance with Richard III ensured his acquisition of the title. The first creation of the dukedom had gone extinct with the death of Anne de Mowbray in 1476, and the second creation had just been stripped from her widower, Richard of York, only three days before Howard received the title.
At Richard III's personal request, Howard took the nine-year-old Richard of Shrewsbury, Edward IV's younger son, from Westminster Abbey where the boy was in sanctuary, and delivered him to the Tower of London to join his brother Edward V. Both boys subsequently disappeared in mysterious circumstances.
Yes. King Edward IV knighted Howard on the field at the Battle of Towton on the 29th of March 1461. That same year Howard was appointed Constable of Norwich and Colchester castles and joined the royal household as one of the King's carvers.