I'm not sure whether these answers are 100% correct, but I hope they help. Academic English = usually taught at school/university/college level; includes English used in textbooks, prescribed literature/poetry books, etc. Business English = used in the workplace; phrases that are not commonly used in casual English conversation, such as, 'service level agreements', 'productivity rate', or 'appetite for spending', etc. General English = what you are taught when you are learning to read and write English for the first time, eg. correct grammar, sentence structure, spelling, punctuation, etc. I hope this helps :)

In my opinion, Business English is one level higher.

Academic General is broad. It is English used for many subjects without being an expert in any, but only on essay writing. Business English is focused on business, and highlights the importance of what business words in English is appropriate for business people and people who has business interests.