Short answers, pulled from the story.
South Vietnam existed from 1955 to 1975. The State of Vietnam withdrew from the French Union on the 20th of July 1954, and General Dương Văn Minh unconditionally surrendered Saigon and the rest of South Vietnam to North Vietnam on the 30th of April 1975.
Ngô Đình Diệm declared himself president of the newly proclaimed Republic of Vietnam on the 26th of October 1955. Later leaders included General Dương Văn Minh who became president after Diệm was overthrown in a coup on the 1st of November 1963, Air Marshal Nguyễn Cao Kỳ who ruled until late 1967, and President Nguyễn Văn Thiệu who resigned on the 21st of April 1975.
The Huế Phật Đản shootings occurred on the 8th of May 1963, leading to a Buddhist crisis that provoked protests and civil resistance across South Vietnam. Special Forces raided Buddhist temples nationwide, leaving a death toll estimated in the hundreds.
Electrical production increased fourteen-fold between 1954 and 1973 while industrial output rose by an average of 6.9 percent annually. Rice output increased by 203 percent and university students grew from 2,000 to 90,000 during the same period.
The People's Army of Vietnam and Việt Cộng broke the traditional truce accompanying the Tết holiday on the 31st of January 1968. Fighting peaked during the Tet Offensive of February 1968 when over a million South Vietnamese soldiers, 500,000 U.S. soldiers, and 100,000 soldiers from allied nations like South Korea, Australia, and Thailand were present in South Vietnam.