Ten questions and review of Avatar

I feel that Avatar is a very good movie as it features the ugly side of human nature and also is a movie full of exciting adventures, and much more can be experienced when watching the 3D. Even me, who usually does not have much interest for adventure-packed shows, liked the movie very much. The storyline is also very exciting, and my favourite part is where the war broke out between the two planets, Earth and Pandora. It somehow makes me excited to see war between two different species.
This movie is mainly about the Earthlings trying to gain a type of valuable resource called the 'unobtainium', which is found on the planet of Pandora. Thus, humans have tried many different ways, and finally came up with a machine which could transfer a person's mind into an 'avatar' body. At first, they are using the people to try and negotiate with the Na'vi, the natives of Pandora, to relocate their home to elsewhere such that the extraction of the unobtainium from the ground directly under the Na'vis' home will not affect them. However, since the negotiation fell through, human had to resort to force to forcibly take the unobtainium, which triggered the war between the two planets, which is the best part of the movie. The way the war was fought was very exciting and thrilling, so, I would recommend this to people of all age group, and this is definitely not one that you would want to miss!

Here are the 10 questions about Avatar which I am curious about:
1.When Jake Sully(human form) was dying because of the lack of oxygen on Pandora, how did Neytiri(Jake Sully's Na'vi ''girlfriend'' in the movie) actually know that the human she saw was Jake Sully?
2.How did Earthlings got to know about the value of unobtainium?
3.We know that the Na'vis were taught English by Dr. Grace Augustine, but to do so, she must understand the Na'vi language.So how did they manage to understand what she was trying to teach them?
4. Why wasn't Jake Sully able to have an artificial leg transplant so that he would not be reliant on wheelchair for movement?
5. How did the military helicopters get to Pandora if it was not a part of Earth?
6. What is the longest time possible which a human can stay on Pandora in the 'Avatar' body?
7. Are there any side effects on the body if a person frequently goes into the 'Avatar' body?
8. How did they manage to get an 'Avatar' body for the human to transfer to in the first place?
9. How does one know if he/she is compatible with an 'Avatar' body?
10. Why was the wheelchair of Jake Sully seemed like those in modern times even though other forms of technology has improved by leaps and bounds?