Gender, unlike sex, is a social construct with little to no basis in human biology. So the obvious answer is number 4.
Well I would quibble with that. I'm pretty sure that though the means by one which expresses their gender is a construct, gender identity is rooted in biological reasons. When children with indeterminate genitals at birth have been raised as the opposite gender (including an infamous case of psychological mispractice) they often in adolescence display signs similar to Gender Dysphoria in trans individuals.
Anyway, my instinct is that I have little inclination to be thrown into an asylum or whatever (I have enough problems with self-esteem without having to wear hospital gowns all day :/ ) so I lean against the second option. The bathroom debate makes me cringe. Mostly at the GOP seeing as the average Republican congressmen s probably a sex predator themself, so it feels a bit like projecting.