Question: is plastic man and elongated man the same

Answer: No, Elongated Man was created by writer John Broome and penciler Carmine Infantino, with significant input from editor Julius Schwartz, who wanted a new supporting character for the Flash. Despite the acknowledgement that Schwartz did not realize DC owned the name Plastic Man (acquired in 1956 along with other Quality Comics properties), Infantino and inker Murphy Anderson stated that he never used him as a reference for anything.