I loved reading that thread, I really did. You seem to be on the right path with the right mindset. But I need to correct you on a few things. You say you'll devote the next 10 years of your life to become a master at this game. The reality is, you must devote your entire life to it. A true hacker learns new stuff each and every day. Also you can never master this area. No matter how hard you try, there will always be someone better. You are a noob. You will stay a noob forever. Look at my signature and you'll understand. Snayler says, "The more you learn, the more you'll realize you know nothing." That's because the knowledge we have is only a fraction of the knowledge that exists. Which is practically infinite. So we have zero knowledge, no matter how much we know.
Now, for your Questions:
a) IYO, Is the learning course I have stated above valid ?
Yes, it is valid to get you to the bottom wrung in the field. The knowledge that all of us have. From there, you're on your own and have to keep learning till you die.
b) Is it possible to make this journey on your own- without a real live mentor and/or institutionalized assistance eg. a college?
Yes it is. Whatever we are, it is because of us, and us only. As Lucid said, "This is strictly DIY or GTFO.
c) I am 24yr old; Point blank: Do you think I am too old to start learning this from scratch?
You are never too old and never too young to start learning anything. You'll be learning till the day you die. Don't ever think someone younger than you can't teach you something.
Look at me, I'm 13.