I have a lot of questions, not meant to detract from the movie, because I think it was one of the best movies in recent memory. I just need some clarification. SPOILERS SPOILERS SPOILERS
There may be obvious answers to this, I'm so confused tying things together, that sometimes I lose hold of the obvious stuff, so please be patient with me. I'm going to try to break down the climax chronologically, because I see some inconsistencies that I think Nolan is too good to forget, so I must be fundamentally mistaken about something.
Fischer was shot as soon as he entered the snow fortress by Cobb's projection of Mal. He then went to limbo, was captured by Mal, who was holding him hostage to get to Cobb, and then he awaited revival, seemingly dead, on the snow level. Saito died considerably later than this, much later factoring in time differences in each dream level.
As for Cobb, he and Ariadne left the snow level and went into limbo to find Fischer before Saito died, where they met Mal in their house. If Fischer was in limbo so long, why did he still appear as his young self when Ariadne found him and kicked him off the building? Saito was there, it seems, for a shorter period than Fischer, yet he became an old man. I accept that after he watched Mal die in his arms, he resolved his guilt and was able to keep her out of his subconscious. But what happened that made him wake up on the shores of his subconscious? Isn't this the same limbo in which he and Ariadne just killed Mal? Did he pass out from the stab wound and wake up still in limbo, but in the place where he always starts? He couldn't have died, because I think that would have woken him up. At least that's how he and Saito wake up in the end.
Ariadne was about to shoot Cobb to wake him up, but then he said he was going to look for Saito. So after kicking Fischer off the building to initiate his kick, she herself jumped off and left limbo. So those two went back up to the snow level. That means Eames, Ariadne, Fischer, and Saito's dead body were on the snow level (Eames' dream), Arthur was on the hotel level (his dream), and Yusuf was physically in the van as he drove it off the cliff on the rainy city level (his dream).
Are the waking up rules basically this?: First, you need to sync up kicks on every level for every person with the Edith Piaf countdown; the lower the level you're on, the slightly sooner your kick must be (Ariadne and Fischer fell off the building in limbo to enter the snow dream, Eames jump-started and awoke Fischer as he fell off the building in limbo, moments later they exploded the fortress and fell into Arthur's dream just as Arthur dropped them in the elevator, which pushed them up to Yusuf's dream.) Then, Arthur, Ariadne, Fischer, and Eames (disguised as a projection of Fischer's godfather) escaped the sinking van. Did this kick push Yusuf up a level into being fully awake on the plane, since the furthest level he dropped to was his dream (the first one)? Or did he also escape the van under water in his dream? I can't remember, but either way, it raises questions for me. If he was still in the van underwater, does that mean only the timer can awake people from the first (Yusuf's) dream? And if Cobb and Saito shot themselves in limbo to wake up, were they somewhere in one of the dreams until the timer went off? It appears they awoke a little later than everyone else, but does that mean the timer didn't wake them up?
Since they were under such heavy sedation, they would fall into limbo if they got killed on any of the three dream levels. But in limbo, if you die, do you just wake up? Because that's basically how Cobb and Saito woke up back on the plane. Why didn't Ariadne just shoot herself and wake up after kicking Fischer off the building? Or maybe she didn't understand the rules of limbo? Also, I can't remember, did she reawaken on the snow fortress level and wait for Eames kick of blowing up the fortress, or immediately enter Arthur's dream in the falling elevator?
Also, in limbo is time completely relative? Did Saito only age because he so frequently referenced dying an old, lonely man, so that is what happened to him. I don't think Mal and Cobb literally got old in limbo, if they did, I don't think they realized their aging. Since it was a dream, they saw each other as forever the same as when they first started the dream. Is this why Cobb could be in limbo so long without aging, because he didn't imagine himself aging? Because, think about it, based on the snow fortress level time, he went into limbo about five to ten minutes after Saito at most. Then, for about five to ten minutes snow level time, he and Ariadne walked through Cobb's old 'subconscious neighborhood' before reaching Mal. Factor in time spent talking with Mal, watching Mal die, and doing whatever he did to wind up on the shore, and he was in limbo for long enough so that if Saito was that old, he should at least looked half as old if not as old as Saito.
Good luck answering these, they're really poorly organized and some may not make sense, but I just typed questions as they popped in my head. I think I must have forgotten some parts of the movie, so please correct me if my sequencing or something else is wrong.