Towards the end of the film, Tony Stark had the fourth ring, yet when he destroys the Earth Spirit all four rings fall to the ground with it's mask.
The "demon elementals" are earth, fire, water and air - Western elements. The traditional Chinese elements are earth, fire, water, wood and metal.
A cargo plane with a wanted fugitive traveling from New York to China should be very easy to catch for a group like S.H.I.E.L.D.
As Tony Stark flies out of the volcano and crashes, the forest is clearly a flat multi-colored plane and not the top of a forest.
When Li Mei leaves the room after Tony Stark awakens, she visually knocks the door twice but only one knock sound is heard.
With Li Mei and the Jade Dragons all dead, there would be no one to prove to the Chinese government and S.H.I.E.L.D. that Tony Stark was not arms dealing.
Tony says the life-support device makes him "look like Frankenstein." Frankenstein was the creator, not the monster (though this is a common mistake).