Short answers, pulled from the story.
NASA officials approved the development of the Rocketdyne J-2 on the 1st of June 1960. This approval followed a source evaluation board selection from five bidding companies after the Saturn Vehicle Evaluation Committee report in 1959.
The Rocketdyne J-2 engine produced 13,000 pounds of thrust using fuel turbopumps operating at 27,000 rpm and oxidizer turbopumps at 8,600 rpm. The first production engine achieved a full-duration static test of 410 seconds in December 1964 with accumulated operational time reaching 3774 seconds.
The Rocketdyne J-2 engine could restart once after shutdown when flown on the Saturn V S-IVB third stage to perform translunar injection. Gaseous hydrogen start tanks refilled during previous firing while ullage rockets settled propellants to ensure liquid head to turbopump inlets before re-ignition occurred.
Development of the Rocketdyne J-2X ceased officially after prototype testing ended in 2014 following President Barack Obama's cancellation of Project Constellation on the 11th of October 2010. Planned upper stage selection eventually favored an RL-10 variant instead despite successful gas generator designs emerging in September 2008.
The Rocketdyne J-2 thrust chamber assembly consisted of thick stainless steel tubes stacked longitudinally and furnace-brazed into a single unit with a bell shape expansion area ratio of 27.5 to 1. Regenerative cooling utilized fuel entering from a manifold located midway between the throat and exit at pressures exceeding 1,000 pounds per square inch.