Short answers, pulled from the story.
Liquid Snake is a fictional character and antagonist from the Metal Gear franchise who was created as part of the Les Enfants Terribles project to clone Big Boss. He is the brother of Solid Snake and harbored deep resentment toward him due to his belief that he possessed flawed genes.
Liquid Snake died suddenly when he succumbed to the FOXDIE virus injected into both brothers after being defeated by Solid Snake on Shadow Moses Island in Alaska. The virus targeted victims based on specific DNA, leaving Snake doubting his own survival after Liquid's demise.
Eli operated along the Angola-Zaire border region in Central Africa where he led a mercenary unit called the White Mamba. He later fled England at age twelve and fought against Venom Snake in Masa Village before escaping with the Third Child to an unnamed African island surrounded by saltwater.
Liquid Snake survives through transplanted body parts and consciousness transfer techniques where his right arm was grafted onto Revolver Ocelot allowing his voice and mannerisms to emerge. By Metal Gear Solid 4: Guns of the Patriots his consciousness seemed to inhabit Ocelot entirely under the guise of Liquid Ocelot until it was revealed to be self-hypnosis orchestrated by Ocelot himself.
Banjo Ginga provided Liquid Snake's Japanese voice in the original Metal Gear Solid while Cam Clarke voiced him in English under the pseudonym James Flinders for PlayStation releases. Both actors reprised their roles in Metal Gear Solid 2: Sons of Liberty alongside stuntman Mark Musashi who performed motion capture for The Twin Snakes remake.