What were the following people to do with the films mentioned:- Troy Porter in ET; randy Morton in Along Came a Spider; John J Slatsky in Seventh Sign; Octavio Molina in Boomerang
According to the Internet Movie Database, all the individuals you mention have technical jobs in movies (sound, art, costume, props); but they didn't work on the films you mention.
IMDB quite often lists actors and support people who weren't credited in the original movie, though, as you will be aware, in recent years the credits themselves have become incredibly long. Presumably however, the people in your question MAY have worked, uncredited, on the films you mention - but what makes you think so?
If they didn't work on the film why would a quizsetter ask the question. There are ten of these such questions and I have 6 of them, so I assume the others did work on them. IMDB often miss persons who have worked on a film yet they appear on the credits of the Video or DVD. I'm assuming that is what has happened here.