When Troy is attacked by the guards at the prison, he dodges behind a box marked "Ingen". That's the company that cloned dinosaurs in Jurassic Park (1993). "Ingen" also means "no one" in Danish, Norwegian and Swedish.
On the runway, when Castor arrives in his car, he is wearing three gold rings - one on his right hand (ring finger) and two on his left (pinky and middle finger.) In the plane, a clear shot of one of his hands shows that he is wearing a ring on his pinky only. Whichever hand this is, right or left, it is inconsistent with the previous scene.
When Castor Troy (C. Troy) and Sean Archer (S. Archer) are having their faces switched in the laboratory, the monitor for Castor Troy shows his name as "T. Castor". When in fact it would read either "Troy. Castor" or "Troy. C". Hospitals/ Institutions always record patient details as: Surname. First Name / Initial.
Just before Dubov gets shot by Walton, we see Burke Hicks running up to Walton to try to stop him. A few minutes later when Dubov falls down and Walton tries to shoot Castor, Burke Hicks runs up to Walton again.
Did Sasha know in the end that Archer and Castor had switched identities?
A
It's hard to say however it's apparent that she realized that something wasn't right. It was definitely strange that the man who looked like Sean Archer was pointing a gun at his own wife and the man who looked like Castor Troy was pointing a gun at his two bodyguards. Even if she did figure it out she obviously chose to side with Archer. Even though she hated Archer for threatening to take her son away for refusing to give up information about Castor she hated Castor even more for walking out on her and for the evil person he had become. Furthermore she knew that the man who looked like Archer had murdered her brother and the man who looked like Castor had opened up to her and showed genuine concern for her son, probably the only person in her life who had ever done so.
Q
What are the differences between the BBFC-18 DVD and the uncut version?
A
The scenes involving a butterfly knife were removed from the British BBFC-18 DVD. A detailed comparison between both versions with pictures can be found here.