Chapter Four: The Body - S1-E4
Question: Where did the body of Will come from? And why was it stuffed full of cotton?
Chapter Eight: The Upside Down - S1-E8
Question: I heard that Steve was originally supposed to die in this season. Was it during the fight against the Demogorgon?
Answer: Technically Steve was never intended to die in Stranger Things. The Duffer brothers wrote a pilot script for a miniseries called Montauk that would eventually become Stranger Things. In that version of the story Steve is a more overtly villainous character and is killed by a monster. The Steve character was reworked once Stranger Things was created due to Joe Keery's more likeable approach to the character.
Answer: No. Steve has not died in any of the 3 seasons so far.
Answer: The body was fake, made by the scientists at Hawkins Lab in an attempt to cover up his disappearance and the existence of the Upside Down.