I am trying to figure out the same thing about my turtle. I found him at the beach (and no he's not a sea turtle) about a year and a half ago, and he is still only about 2 inches big. But anyways the only thing I have been able to find out for sure is that if it has a red stripe on its cheak then it is a red eared slider. but this website might help: http://www.turtlecare.net/what.htm
yes
Sea Turtle
It depends on what type of turtle it is
Sorry, but you need to describe your turtle.
4 feet Actually it depends what type of turtle, how old it is, and if it is sick...
Green Sea Turtle
I don't know. It sometimes depends on what type of turtle it is.
it depends on what type of turtle and how heavy it is
sea turtle like in water
a type of leatherback turtle does
snapping turtle is a secondary consumer
Google is probably the best with endless pics of any turtle just type in pics of turtles or your specific turtle type