How old girls can I approach?

I'm a 14 year old boy and I'm wondering how old girls I can approach. I know I can approach 14 year old girls, but could I for example approach 16 year old girls? I don't mean if they would be nice to me, but if they would be willing to be friends with me. Because I know if I approach a girl in her 20s she may be friendly, but of course she would not be friends with me because she would almost be 10 years older than me. So how old girls can I approach that would be friends with me? Because if I'm at a mall or something I'm only looking for girls who is 14 or younger. So hope you can help. Especially you girls who are 16, 17 years old. And say what you would do.