They can be taught to talk, yes.
Yes the green cinnamon can breed with the green cheeked conures.
GCC's are generally quite nippy birds but you can get ones that aren't. It depends on their personality. I have one that is nippy sometimes but usually he is fine.
No, not quite sun conures are a little larger than green cheek conures.
One way to tell if the Patagonian conure is male or female is by looking at the birds head shape. A female conures will have soft round head while a males head is more flat. Most female conures have pink feet while males have grey feet.
the amazon
The Green-cheeked parrot's habitat is found in South America, in the forests of Mexico, Brazil, Bolivia and Argentina.
Green cheeked parakeets are currently not endangered. Most likely because there is strong enough numbers and no hunting.
a jaguar
They eat fruit
3000-6500!
7,564 years old
There is a huge difference in size. Sun conures and Green Cheek Conures are both small parrots, only slightly bigger than parakeets. An Amazon is a medium sized bird and will most likely kill the smaller Conures.