reserve officer training corps
Yes, all majors are accepted by ROTC
Yes, there is my friend who lives in Hawaii talks about JROTC and ROTC all the time.
Embry-Riddle has ROTC for all 3 branches
No, not at all.
Yes. JROTC is in high school, ROTC is in college. Technically, you do not have to take JROTC at all to take ROTC. Generally, people who take ROTC in college are joining the military afterwards. The same in not necessarily true for JROTC.
Yes.
teach ROTC
Admin commands can vary widely depending upon what script you are using. Some admin command scripts let you view a list of all commands by typing "commands/". Other command scripts provide a list of all commands in the comments of the script itself.
Students who are contracted ROTC cadets pay for very little in college. A full ROTC scholarship includes: tuition and fees, $600/ semester for books, and a monthly spending stipend of $300-$500 a month. Also, ROTC classes are available to all college students for free and no military obligation.
The end of mandatory ROTC
Unless you enlist you will not go to AIT for ROTC. The enlisted side and officer sides of the military have different training schools. After ROTC you will go to BOLC (Basic Officer Leaders Course) A and B. A is like the officer Basic and B is like officer AIT.
That's similar to asking Why not have every song built in to my stereo? There are many different sources for commands, and new ones are coming out all the time.