I don't believe it is possible to be 'gay' before puberty. It is the onset of hormones that typically drive one to figure out their sexual orientation. Some people may feel they are in the wrong body from an early age, but that is driven by puberty.
Yes, hair growth is normal for a boy going through puberty. However, at 13, I very much doubt you're at the end of puberty. Most males end puberty at around 16 or 17.
it goes straight to the dump.
you may get muscle growth any time from now until about a little before you end puberty. some effects of puberty come out really late in some people
The brain is usually fully developed by the end of puberty. There is not much increase in the weight of brain after puberty is over.
A straight line with arrow in the end
Generally anywhere between the ages of 10 and 18. The most common age is 12 1/2 though. Some females never go through puberty.
Puberty
You are not late. Everyone has their first "real" ejaculation at different times, there are people who may not ejacualte till they are married. And no you are not near the end of puberty. Puberty normally lasts till around the ages of 18 and 21.
Unfortunatley you cannot predict when you will finish puberty nor can you predict when you'll start.
People normally do not grow after puberty unless their pituitary gland is out of control, with the exception of gaining muscle mass through exercise (or getting fat from lack of exercise and a poor diet).
Overweight children do tend to hit puberty earlier, but they also tend to end puberty earlier.
Yes, puberty is a discontinuous development. The body may grow to a more extent at the onset of puberty than towards the end or vice versa.