The planet from prometheus is the same planet in Alien. If its not, than the warning beacon that Shaw left on 223 had to have been moved to some random planet. Theres no evidence that supports that theory so it is obviously the same planet.
Also, robots are unable to feel emotions, so how could vickers be a robot if she clearly panicked and got scared when Janek decides to go kamakazi into the alien spaceship.
None of your theories can be clearly supported by facts.
By Leonard Gill
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