There are stories of kids telling their parents how they feel and stopping female puberty before it goes ahead. To then be prescribed T and go through a male puberty only. I think it's possible...
There was a story on 20/20 about Jeremy go to
http://abcnews.go.com/2020/story?id=3078716&page=1 that is the letter he wrote to his parents but the story is there somewhere - have a look worth a read I reckon...
As for what does T do –
shuts down your ovaries eventually so you wont be able to reproduce, basically all those organs atrophy and become useless sort of lay dormant in your body
you become susceptible to medical issues similar to that of men your age but still are susceptible to things like breast cancer and dependant on hysto or not ovarian and other cancers down there
it changes the fat distribution to more of a male pattern
you can lose your hair
your muscles become more dense
the angle of your jaw can change to look more masculine
you become broader etc and
your 'clitoris' (I hate calling it that) will enlarge and look and behave like a small penis
you will also experience emotional changes - it becomes harder to cry and express emotions for most guys and there are others too...
It doesn't just give you more hair and a deep voice mate. It does affect you physiologically. Google is your friend or try wiki – full of information if you want specifics.