6. My vaginal lips are long and stretched-looking, sort of hanging down like a chicken’s neck. Could I have done this by masturbating too often or too hard as a teenager?

No. Your vaginal lips, or labia, are not like your neck-the shape isn’t affected by too much sun, too many cookies, or too much sexual pleasure. You can’t change their shape, because it’s hereditary. But how many women are able too look at their mothers’ vaginal lips to learn about their heritage?
Labia are like noses. They all share the same structures and over all appearance, but each one is unique, exactly, like no other. Thus, your concept of what labia “should” look like is arbitrary. You can see drawings of wide variety of “normal” vaginal lips in Betty Dodson’s wonderful book, Liberating Masturbation.
Your “chicken neck” lips are not problems. Not only is there nothing wrong with them; in some cultures such lips would be prized. Rather than thinking of your lips as “long and stretched,” can you think of them as having a “come kiss me look?