I'm mostly self-taught. When I was very young (kindergarten age, if I recall correctly), I attended a few QBasic courses at a local college, took some VB (it was billed as "advanced computer programming") at a summer camp when I was 15 or so, but other than those, no formal training.

I remember writing BASIC on the Apple IIGS computer in my first grade classroom, playing with HTML in second grade, but my big breaks came around 6th iirc. I helped move an online community from a hosted bulletin-board provided (ezBoard) to a hosted phpBB instance, and hacked on that code for a while, but was nothing serious. Write a few scraps of PHP here and there before getting into Python, and did web development in that for a while.

Over time, though, I've followed this gradual descent down toward the metal, learning C from K&R (great book) while holding down a Python/ActionScript day job and occupyng myself outside of work learning how to design C APIs and writing a few libraries. The second-to-most-recent position I held involved Python and Ruby at work, and I contributed some code to the Linux kernel in my free time (some USB audio stuff). The position after that was for Linux kernel development and other low-level embedded systems work. I've tried to get into infosec a few times but nothing's panned out.

Currently I'm getting a startup off the ground (surprise, surprise). Desktop software, audio production, lots of real-time DSP, lock/wait-free data structures, some OpenGL...I'm happy as can be.

To answer your questions:

1/ Totally self-taught from books and RTFM. Lots of help from the Internet as well, though I own my fair share of college texts.

2/ I'm 24 now, started learning around 2001 I think (when I was about 11).

3/ Got my first development gig at 17.