How long is a passport valid
The validity of your passport depends on your age. If you are 16 years or older, the passport is valid for 10 years from the issue date. However, if you are 15 years or younger, it will only be valid for 5 years. http://www.ehow.com/about_4574515_long-passport-good-for_.html has additional information.
5 years or 10 years that depends on the country
8 or 10
Up to the expiration date given on your passport.