Jr. ROTC is not a requirement for joining any military branch. It can be a benefit to you both personally and professionally (although I would avoid sharing this information in Boot Camp if you do join).
JROTC was invented for high school students to see if there would be a better motivation to join the military, and if the students would want to further into the rotc in college to become officers.
College ROTC commissions Reserve, National Guard, and Active Duty officers. You may choose which one you want.
You can pursue any major field of study you want in ROTC. Your major has no affect on what your job in the military will be. My advice is to take the easiest major you have interest in. The higher your GPA, the more likely it is you get the military speciality you want.
You can't join as a captain. You either join as an enlisted troop, get accepted to officer training, become a lieutenant and get promoted to captain, or you join through one of the officer accession programs (the military academy or ROTC), come in as a lieutenant and get promoted to captain.
Easy...join the military dummy.
You only need a degree if you want to be an officer. You can either go to school on your own to obtain a Bachelor's degree or join an ROTC program which will have a contract for service upon graduation
There's nothing worse than a soldier with a severe ego problem. You just need to be the best you can be.
18 years old is the minimum age required to join the Navy ROTC.
They should, since military school prepares you for the actual military.
English would be a start. The question is very vague. You don't need to take "special" classes. However, you do need at the minimum a High School Diploma. At one time a GED was sufficient. Some of the services do not accept the GED anymore.
As many that are qualified and want to join.
No. Go talk to a recruiter and tell them you want to take the asvab but you arent sure if you want to join yet.