1、
The first thing to note is that the fourth layer is by no means the edge of the subconscious. Be sure to distinguish, otherwise the film can't be understood. The place where Cobb and the little girl entered and rescued Fisher was on the fourth floor (Cobb and the little girl were conscious enough to know that they were in a dream), while old Qi Teng was on the edge of the subconscious (Cobb and old Qi Teng were not conscious enough to distinguish dreams from reality).
Let's talk about their introduction. Qi Teng bled to death and went directly to the edge of the subconscious, instead of going to the fourth floor. Fisher did not die directly after the shooting, but his heart stopped beating temporarily, which can be understood as that his brain did not die, which is equivalent to coma or sleep. So I went to the fourth floor temporarily. If I don't save it right away, I will be on the verge of subconscious when I die completely. The little girl and Cobb immediately entered the fourth floor to save people. In the end, Cobb didn't cross successfully, and he was drowned before he entered the edge of the subconscious. Therefore, Cobb entered the edge of the subconscious later than Qi Teng, and Qi Teng was old. (If we equate the edge of the subconscious with the fourth floor, Cobb will enter earlier than Qi Teng, and Cobb should be old. )
In a word, Fisher went into the fourth floor in a coma, and the hero and the little girl also went in to save him, but Qi Teng didn't go into the fourth floor, and he went directly to the edge of the subconscious. The fourth layer is not the edge of the subconscious.
2. Not because you woke up with a sedative, but because you used a sedative, you will die and go to the edge of your subconscious. The purpose of using sedatives is to have a triple dream.
There is an explanation in the film: a dream without tranquilizer can't be more than three floors, and death will wake up in the dream; A dream with sedatives will reach a deep level, but the death in the dream will not wake up but enter the deepest level of the dream-the edge of the subconscious.
There were three layers of dreams in the last thieves' mission plan (actually four layers were made), so with tranquilizers, people will go to the edge of the subconscious when they die.
People on the edge of the subconscious will wake up directly when they die. Because this is the deepest dream, and it will never fall anywhere again.
3. Wake up after falling is like this: the first floor is a dreamer, and the dreamer will have a real feeling of falling, and the dreamer should have a dream to match this feeling. Kicking feelings+dreams will make people awake. When crossing at the same time, the dream generated by the kicking of one layer is just the kicking of the next layer, which is the reason for kicking at the same time.
On the first floor, everyone woke up. Without kicking on the plane, they wouldn't wake up and go back to the plane. People on the plane don't know when the dreamer will finish the task, so they can only wait for the medicine to pass and let everyone wake up. The fact is, when everyone wakes up, there are still 20 minutes before the plane lands. This task can't take that long. This is the time to work. In fact, on the first floor, everyone waited for another week before they woke up after taking the medicine.
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Supplementary question:
The marginal death of the subconscious will return to reality, which is a rule stipulated by the director or screenwriter. In fact, don't they make all the rules in the movie? But this rule did not suddenly appear, but it was foreshadowing. It was suggested that Cobb and his wife were on the edge of the subconscious from the beginning, and they woke up after lying on the tracks once and returned to reality.