Short answers, pulled from the story.
Robert E. Lee took command of the army on the 1st of June 1862 following Johnston's wounding during the Battle of Seven Pines. The Right Wing was later redesignated as the First Corps with authorization from that same year.
The First Corps started reaching Marye's Heights on November 18 and deployed there to contest a possible pontoon crossing of the Union army at Fredericksburg. Confederate forces under William Barksdale's brigade fired at Union pontooners shortly after 5 a.m. on December 11, forcing them to abandon their work.
Pickett's diminished division advanced against Union positions with an estimated force of 11,000 to 15,000 men. This attack resulted in over 2,600 casualties for Pickett along with the loss of all three brigade commanders and all but one regimental commander.
The First Corps used 16 railroads on a nearly 800-mile route through North and South Carolina to reach the Army of Tennessee due to different gauges of the surviving Southern rail system. This round-about journey took three weeks to complete before the corps opened the Battle of Chickamauga on September 18.
The remnants of the Third Corps merged into the First Corps on April 2 following Lt. Gen. A.P. Hill's death at Petersburg. The corps was disbanded shortly after General Robert E. Lee surrendered to Union forces on the 9th of April 1865.