Short answers, pulled from the story.
The History of The Lord of the Rings is a four-volume work by Christopher Tolkien that documents his father J. R. R. Tolkien's process of constructing The Lord of the Rings, drawing on drafts and manuscripts. It is also numbered as volumes six through nine of the twelve-volume series The History of Middle-earth.
The four volumes were published between 1988 and 1992. The Return of the Shadow appeared in 1988, The Treason of Isengard in 1989, The War of the Ring in 1990, and Sauron Defeated in 1992.
In the earliest drafts, the Hobbit hero was named Bingo rather than Frodo. The Tengwar inscription on the first volume of The History of The Lord of the Rings explicitly identifies this, describing the hero as "at first named Bingo but afterwards Frodo."
The character eventually known as Pippin Took passed through at least eight names during composition: Odo, Frodo, Folco, Faramond, Peregrin, Hamilcar, Fredegar, and Olo. The character was also associated with multiple Hobbit families, including the Boffins, Bolgers, and Tooks.
Sauron Defeated contains two episodes that were cut from The Lord of the Rings: the pardoning of Saruman and an awards ceremony at the close of the book. It also includes a rejected epilogue in which Sam answers his children's questions, and the only surviving account of Tolkien's constructed language Adunaic.
The titles are names Tolkien once proposed for the individual books within The Lord of the Rings itself. Tolkien planned six internal books with titles including The Treason of Isengard, The War of the Ring, and The End of the Third Age; these were discarded when the publisher split the novel into three volumes, and Christopher Tolkien later reused them for the documentary series.