1. See these two sites to help you with the "what is the training?" question.TRACEN Cape May
link to check out the boot camp website.Helmsman
to check out the standards and such for boot camp.
2. Yes, there are quite a few former enlisted who have become officers, with many of those becoming pilots.
3. It's not easy to change jobs once the Coast Guard has spent the money to train you for a particular job. That isn't to say you can't, it's just not that easy. This should not be construed as your job not changing, it does, as you advance through the rates and ranks. As a quartermaster (navigation) my job changed depending on assignment. At an Operations Center (they're now called Command Centers) I would plan Search and Rescue (SAR) cases. On ship my job was on the bridge assisting the navigator to make sure we knew our precise location (rocks and ships don't mix). After changing jobs to radioman my job was communications at one unit, computers at the next and then back to communications. As you can see, the job changes with the unit in many cases.Enlisted careersOfficer careers
Check out the two links above to get an idea of the difference between officer and enlisted.
Caution: I have two brain cells. Sometimes they both work at the same time.