1. I love the Corps, but am incredibly biased. To each his own as it depends on what you want to do.
2. Marine Corps boot camp...13 weeks of hell to become an enlisted US Marine. The enlisted do not need a degree, are underpaid, overworked, and most respected by anyone who knows because E-1 through E-5 pay grades CARRY the entire US military (as that's where the vast majority of the troops are). Marine Corps Officer Candidate School...8 weeks of actual OCS and 18 more weeks of TBS (The Basic School)...so 26 weeks of hell to become a Marine Corps officer. Officers do need a degree, are paid pretty well, work even longer hours than most enlisted, and get almost no respect from anyone until they're an O-3 or so. Also, in terms of the Marines only the enlisted side gets to pick their job (MOS). Officers get to create a wish list but ultimately the Corps picks.
3. ROTC and NROTC are scholarship programs offered through the military that give free education prior to taking your commission as an officer. To get an (N)ROTC scholarship you must have a high grade point average, high standardized test scores, community service, letters of recommendation from community figures (like teachers), be willing to spend two summers doing training for your respective branch, and sign a six year active duty commission. JROTC is a program offered in high school that is supposed to ready you for the vigors of the military. Its benefits vary by area.
4. Special operations, in most cases are an assigned job as part of the infantry. This does not mean you have to enlist as infantry, but each area has its different ways to get in to. That's something a recruiter would have to handle.
Semper Fi and good luck.
PS...Just in case anyone wants to argue with my respect theory I'll clarify now. Even officers respect enlisted...Respect and authority are two very different things (junior enlisted have little authority compared to junior officers).
5. Enlisted promotions are done in the Marines as follows. E-1 through E-3 are done by time in grade (assuming you haven't gotten in trouble). If I remember correctly it takes six months at PVT (E-1) to pick up PFC (E-2). Eight more months to pick up LCpl (E-3) from PFC. Cpl and Sgt are picked up via cutting scores, which are based on time in grade, MOS, PFT scores and a whole host of other things that won't really make sense if I try to explain them correctly (and quickly). Once you hit the staff NCO ranks (E-6 and above) it's done by fit reps. A fit rep is essentially a package that puts your performance as a Marine in perspective compared to another Marine. Fit reps are reviewed by a board, rather than a points system. There are, as always, a hundred other things that can affect ranks and promotion rates like meritorious boards, negative time in grade, NJPs, stop loss, etc...But it's a lot to explain and that is the most common way promotion works. Highest possible rank is SgtMaj of the Marine Corps. He's the head cheese of the enlisted side (like the Commandant of the enlisted, so to speak). He still is, however, an E-9...That's the highest pay grade that exists in any branch on the enlisted side.
I've never given my info before, but I get the impression you're truly interested and I can explain it better if you want more details...sooooo...my email addy is paypalmademegetthis@yahoo (not kidding!) so feel free to email me if you have more questions.