I'll try to give you a reply:
"I will ejaculate for the first time"
Of course you will! In fact, as an average, a male body is ready to do just that since the age of 12, or even earlier.
But if you don't, don't worry, girls love guys that can control themselves
"My penis will get past the 4" when hard-line"
I can't swear, but statistically I would say yes.
I think the world average is 4" ... At least I hope so, because I happen to think in centimeters and I can't swear it when talking in inches.
"I will get underarm hair"
You know, since 99% of mankind have it... yes it will. It might be a little later, you know, that changes from person to person, but yes you will.
Imagine I had a friend who got it at 18!
Hope it helps