I can provide you with some input on your answers.
In the movie "Charade," a mirror is held up to a dead body to check if the person is still breathing. Your answer is correct, as the character is trying to determine if the person is truly dead or if there is any signs of life.
Regarding the believability of the murders in the movie, your analysis is valid. You mention that the murders are not believable because the viewer does not witness the actual act of killing, rather the camera cuts to the scene. However, you also note that some parts, such as when a gun is used, appear real. This is a good observation and shows that certain aspects of the murders may be realistic while others are not.
Regarding the possibility of dying from a fall like the one in the theater, your answer is partially correct. You mention that there was a huge gap between where the character fell from and where they landed on the ground. This could indeed be a factor contributing to the character's death. However, there may be other factors to consider as well, such as the height of the fall, the angle of impact, and the presence of any structural hazards at the landing site.
Finally, your question about the scientific challenges that modern movies would face if "Charade" were made today is interesting. You mention specific scenes where an individual comes back to life after a fall or drowns. In terms of scientific challenges, filmmakers today would be expected to provide more plausible explanations for such occurrences, as modern audiences are more discerning and expect a certain level of realism. This could involve exploring the concept of suspension of disbelief or incorporating technology and special effects to depict these events in a more believable manner.
Overall, your answers are thoughtful, and you have provided valid reasoning for your responses. Keep up the good work!