Can you just self study and take the IB exams. They say they are helpful for British school. Are top US schools interested? I am just curious. As the name implies I am a tutor, not a student.
No, IB must be taken within a certified IB program, because there are exams (called Internal Assesments or IAs) which are teacher graded and are a part of the overall IB grade.
No. I am not being rude, but first of, you can’t just TAKE the exams and pass. They require A LOT of work. Secondly, each subject has internal assessments that must be completed and can take months. Also, if you are interested in the diploma, Extended essay and TOK need to be completed as well. Hope that helps 
As stated above, IB courses require you to take the course to register. AP courses, however, do not, and you can always take an AP test if you’re extremely confident in a subject and are looking for credit.