Height

I'm 6'4 and 15 years old and I wanted to know did I stop growing and if I did'nt can I be 6'10 when I turn 21

Maybe and maybe not! Different people grow at very different rates and untill very different ages. You could very well make it all the way to 6'10 or you could stay right where you are at. A lot of it depends on genetics and how tall the rest of your family is. Whatever the case is, I hope you like basketball!

Girls usually have growth spurts at 12 yrs of age and it contiues slowly after that or may stop altogether just as macenroe2007 said..maybe maybe not so just wait and see. Gosh I wish I was that tall!

i would ask ur doctor they should be able to tell u if u will still be growing or not