1. Yes and no, it means that you don't feel like you are your biological sex
2. It's about how you feel inside
3. Yes, a female who identifies as a man is a man, and, they can act differently if they want
4. Anyone who identifies as a female
5. Sex is usually categorized as female or male but there is variation in the biological attributes that comprise sex and how those attributes are expressed. Gender refers to the socially constructed roles, behaviours, expressions and identities of girls, women, boys, men, and gender diverse people.
(I am trans myself, but I am still not 100% sure)