Question about actors in ANH

During the filming of the original Star Wars film, did the actors know the full story about the rise and fall of Anakin? For instance, when Alec Guinness does the scene where he lies to Luke about his father, does he realize that his character is lying? When the guy who plays Tarkin says the emperor has swept away the last remnants of the Old Republic, does he realize how important that is? Just thought I would ask.

 

Catagorically the answer is no. Actors are given the basic foundation of the story, which at the time of ANH was not fully formed.

There's an important point to make here and it covers several aspects of the making of Star Wars.

Remember the first movie was Lucas's attempt to recapture the love of movie archetypes, the movie serials from the 40's and 50's, the swashbuckling pirate swordplay, the daring hero, the visceral hateful villian, the easy note of good vs. evil by the faces people wore, and the strange customs of a society inspired by Japanese samurai movies, particularly Kirusawa. There was not a lot of talk by the actors about expanding the back history of each, because it had not come to full fuition in 1977. It was all in Lucas' head.

Specifically talking to your points, Obi-Wan didn't lie to Luke at all. From his particular viewpoint, when a Jedi betrays himself and turns to the darkside, one turns your back on all your postive teachings and trainings, you extinguish your honor, civility, and path to good and nonviolent knowledge, and your persona of good is fully relinquished.. In effect, one kills ones self. If Sir Alec Guinness knew that at the point of ANH that he was lying, it's really only at that point he had a part to play and the backstory was not built yet, it was from the literal point of view that he acted out his character, definintely not because he knew the history of his character and the plot points. The success of the first Star Wars allowed Lucas to fully expand and explore the culture and society he created. So Only when Return of the Jedi came out was Alec fully aware of the importance of his place in explaining the Jedi view point to Luke. Does it seem like manipulation? Perhaps, but it was not a lie.

When Tarkin says the Emperor swept away the last remnants, Peter Cushing only knew the basics of his character, not the entire sweep of the Star Wars saga. It was still in evolutionary form in Lucas' mind.

No, the actors did not know the full sweep and scope of the history of Star Wars. Even now, if you speak to actors who are still alive who had been in previous movies, they will tell you that not all Star Wars plot points to this day have been revealed, and they still speculate on the outcome of all the details.