if I were you I'd probably ask the teachers at your old school if they have any material (revision sheets, booklets with answer sheets, textbooks you can borrow) for you... wrt the syllabus, as long as you are genuinely interested in chemistry you should be able to teach yourself all the relevant information from looking up the curriculum, going to the library and googling topics to understand them - and then using pastpapers and markschemes to get the correct wording and the such... although chemistry is probably the hardest subject that you could teach yourself!!
I think you have to participate in practicals on all boards, so you'll probably be better off finding a college or a school that would let you conduct the exams there. as for registration, no idea i'm afraid! good luck