At the end a gender, any gender. Is a sum of behavioral characteristics.

This doesn't really align with my experience of gender. Which is to say, I think what you're describing here is a large part of gender, but it doesn't encapsulate it completely. I'm trans, yet I've never had a strong sense of "femininity" or "masculinity". I don't really "get" gender expression, except in so far as it's a tool to have people see my gender. I certainly don't have a sense of it being tied to my internal experience of my gender. Yet for all of that, I've always had a strong sense of gender.

In a genderless world, I don't think we would all be genderless in the strict sense of the term, but more, our internal experiences of gender would be assumed to be unique, and as such, not really something that can be grouped in to labels and compared to other folks. In this world, what we now call gender expression, would just be self expression.