I am a little confused about what you mean by apply for Legendary? I don't think anyone needs apply or need approval from the admin to become Legendary. If I can remember correctly, during my rank up just works regular activities. Once desired activities achieve then I become Legendary. Whatever post you make above 14 per week, only 14 activities will add to your profile and that's how I become Legendary. I am not aware of any other logic since I hadn't get the advantage of that.