We should push back at every opportunity at the atrocious “sex assigned at birth” nonsense.
Gender is determined at conception. The zygote starts out with either XX or XY chromosomes then, not “at birth”. Minus a minute number of genetic abnormalities, which is not really what we’re talking about here. What we’re talking about here is gender dysphoria.
Yes
The only things assigned at birth are your name and your SSN.
You can legally change your name. I’m not sure if you can change your SSN.