I am not sure if you can answer all my questions, but I will start with one or two.
What is the normal size for my penis if I am 11 years of age?
Is it normal that I get stiffies all the time? I sometimes get a stiffy in the bath, or in the pool, or when I wake in the morning. Is this OK? I often get stiffies when I swim with the other boys at school. Is this OK?
When can I make milk? How old should I be when I can first make milk? How do I do it?
There is no "normal" size for a male penis during the teenage years. You are in the years of growth, but every person grows at different times and at different rates. The best I could tell you is bigger than a child since you have already passed puberty and less than adult since you haven't completed your growth.
From your age and the nature of your questions, I am guessing that you are in stage 2 of development. What you are calling "stiffies" are also known as "boners" or more properly "erections." The ability to have erections start in stage 2 and will continue for the rest of your life. However, because your body has a new ability it takes a while for your brain to figure out how to control it. What you are having are called "spontaneous erections." Big words meaning that you are having erections which you cannot control. You will have them a lot for the next few years. Eventually they will begin to slow down. But even into your twenties there will be moments when your penis will suddenly decide to get erect -- usually when you find it most embarrassing.
Erections in the morning are something every male has. You will have them for the rest of your life. Actually, males have four to six erections every night as you sleep. You just happen to notice the last one because it happens as you wake up. While you sleep you go through cycles of lighter sleep when you dream and deep sleep. The erections come during the periods of lighter sleep. Think of it as your body going through a systems check to make sure everything is working properly. When you get old, if you stop having morning erections for a period of time, it probably indicates that there is something wrong with your body and that you ought to see a doctor.
The hard thing about spontaneous erections is that your fellow students will tease you about them if they notice. This is because at your age it is very easy to get embarrassed, especially about private matters which you barely understand. Also children your age are merciless in finding anything to tease another person because it makes them feel like a bigger person. The way to handle these teasings is to hide your embarrassment and pretend that it doesn't bother you. If they don't get a reaction out of you, they will stop bothering you. Even better is when you can turn the teasing around. "Yeah, it is getting big, isn't it. You probably wish yours was this big."
When you have a morning erection, just make sure you don't bend it forcefully. If you need to use the toilet, wait until it starts to fade. Your body can't hold an erection for more than 30 minutes anyway and most spontaneous erections don't last for more than a few minutes.
What you call "making milk" isn't really milk. What males produce is semen. You will start ejaculating semen when your body grows enough to start producing semen. For about half of all boys this happens late in stage 2, for the rest it happens in stage 4. Again, there is no particular age. It all depends on how your body grows.
In regards to ejaculating semen, that isn't something that you need to do anything particular about. Ejaculation is a part of your body's instincts. When it does happen, it will probably catch you off-guard and surprise you. Just before it does happen, you will have an overwhelming urge to touch and rub your penis. For some boys this happens at night during a dream and it is called a "wet dream." For others it might happen when bathing. When it does happen, just clean it up and wash off any that gets on you.