Yes, they are, but of course they require proper cooking. There are many recipes that call for the use of kidney from various animals, including cows and pigs. I enclose a link to further information about how to cook pork kidney, for example.
There are several different organs in an animal that are considered edible. These organs are called the kidneys, liver, heart, brain, and stomach.
Yes
White Oryx
Renal arteries and veins service an animal's kidneys.
a fork and knife
Antelope
A whelk is a large, edible, marine snail.
Probably alligator.
Edible means "able to be eaten". It refers to foods and substances that can be consumed and digested by a particular animal or insect.
the heart the brain and the kidneys
you can't. it's not possible.
big marshmallow