Sex and gender are two separate concepts. Sex = biological parts; Gender = mental/social aspects of being male or female (which are the polar ends of the spectrum). Gender has a larger spectrum than sex and because it's so wide, there are a lot possibilities regarding where someone can fit into it.

You inherit race and the cultural aspects that come along with your ethnicity as these things are passed down from generation to generation. You do not inherit gender. The term "transracial", if used correctly, would refer to someone who was raised by parents of a different ethnicity, thus inheriting cultural practices etc. It does not refer to people who apply a bunch of self-tan lotion (for example) and then appropriate the experiences of another culture.

It is not possible to change your age because age is linear.

Also, the new DSM has been updated to explain that gender dysphoria is something that trans people may experience (dysphoria = distress). It is not a condition that makes you identify as a gender that is not the same as your biological sex.