Can you let me know how many years of puberty there are, like how many years of changing? I heard that it's about 8 years for males. I also read that males stop growing until about 21. Is it possible to stop growing in height at age 15?
A similar question was asked a while back. See: "Am I done growing?"
The typical male (not all males, just the majority of males) takes between 8 and 10 years to complete all the physical changes between a child's body to an adult's body. Not all those changes involve height. There are changes in muscle mass, shoulder width, hair, and numerous other changes. The 8 to 10 year range doesn't include the changes which take place in the brain, which typical take an additional 4 years. Since they are not seen, they are typically not counted.
The start and end of those changes vary between individuals. Normal is considered anything between starting at 9 to starting at 16. Thus the ending also is variable, based on both when a person starts and how fast they change.
Technically puberty starts in boys about one year before any external signs can be seen. Puberty officially is when your hormones rise in your blood, but that is rarely checked. Typically we call puberty when the first external signs are seen and the range from 9 to 16 is based on that.
If a boy started early, say at age 8 for the first signs and developed quickly, it is possible for him to have a full-adult body by the age of 16. But he is not likely to grow much, if any, in height in that last year as most of those changes involve other characteristics.
You don't see a large number of men develop that soon. It would be called "precocious puberty" by a doctor if he is aware of it. Precocious refers to a person or an animal who develops sooner or faster than what is considered normal. I had a boy in my Tae Kwon Do classes who was fully developed, and towered over me, when he was barely 14. It doesn't typically happen, but it can happen. Whether this is true for you, only your doctor can actually say.