It all depends on genetics Some as young as nine and others not until they are 18. however on average somewhere between 12 and 15,
Around 10-14
Boys start to grow pubic hair from about ages 9 - 12, but, don't worry, different people grow and mature at different rates.
Yes.
Generally after your testicles have started growing to produce large amounts of testosterone that are needed to make a boy into a man.