Short answers, pulled from the story.
Blade Runner was released on the 25th of June, 1982, in 1,290 theaters. Producer Alan Ladd Jr. chose that date because the 25th of the month had been lucky for his previous releases, including Star Wars and Alien.
The screenplay was written by Hampton Fancher and David Peoples. Fancher wrote the original draft, and Peoples was brought in to rewrite it; Fancher later returned for additional rewrites. The voice-over narration in the theatrical release was written by the uncredited Roland Kibbee.
The "tears in rain" speech is Roy Batty's final monologue, delivered by Rutger Hauer before his character dies. Hauer rewrote the speech himself and presented the words to director Ridley Scott on set prior to filming.
Seven different versions of Blade Runner exist. These include the original 1982 workprint, the U.S. theatrical version, the International Cut, and Ridley Scott's Director's Cut from 1992. The Final Cut, released by Warner Bros. in 2007, is the only version over which Scott retained complete artistic and editorial control.
The score was composed and performed by Vangelis, who was fresh from winning an Academy Award for Chariots of Fire. The soundtrack was nominated in 1982 for both a BAFTA and a Golden Globe for best original score, but the official album was not released until 1994.
The film leaves the question deliberately unresolved. Ridley Scott has stated he envisaged Deckard as a replicant, while Harrison Ford and producer Michael Deeley wanted the character to be human. The unicorn-dream sequence Scott inserted into the 1992 Director's Cut, paired with Gaff's origami unicorn, is widely read as implying Deckard's memories are implanted.