I just took MVC and LA as a junior. Do I get credit for them in college?
Also are these classes supposed to be 1 semester or 1/2 school year classes?
I know the next math is Diff Eq; what accredited online program/class do colleges accept as credit?
If they are actual college courses, they may be accepted for credit and/or subject credit, but that depends on the college (keep syllabi, book lists, and exams). In college, these would typically be one semester courses each.
This is completely college dependent. Most schools have AP equivalents, and many have databases for transfer credit from other colleges. You would have to check by school.
Purdue, for example, has Purdue Transfer Credit Course Equivalency Guide if you took it at a college. I don’t know if online sources (JH CTY for example) are included.
Many colleges have ways to test out, and other formal or informal methods for either acceleration or credit.
When I started grad school, the Dean stated at one of the orientations that the official policy was that no courses transfer, but if it was a course at a known/prestigious university, taught by a professor that the dean/professors knew, they “might be able to work something out”.