Short answers, pulled from the story.
The Space Transportation System formally commenced in 1972 after President Richard Nixon met with NASA Administrator James Fletcher. The program concluded on the 31st of August 2011 when all remaining orbiters were retired from service.
Challenger disintegrated 73 seconds after liftoff due to an O-ring failure on the right solid rocket booster. All seven crew members perished in the accident that occurred during mission STS-51-L.
The text does not specify the total number of flights but notes that actual costs reached $196 billion over the thirty-year service life through 2011. Incremental flight costs rose to $409 million per launch by 2010 compared to other vehicles.
Columbia broke up approximately 16 minutes before its expected landing on the 1st of February 2003 during mission STS-107. Foam separating from the external tank struck the left wing leading edge and punctured reinforced carbon-carbon panels which destroyed it from the inside out.
Discovery carried the Hubble Space Telescope into space on the 24th of April 1990 during mission STS-31. Five servicing missions repaired and upgraded the telescope between 1993 and 2009 with Atlantis launching the fifth and final mission in May 2009.