doing gcse at home

hi im at the end of year 10 and i really regret taking one subject and not the other so i wanted to know if i could do a gcse at HOME. the reason why i dont want to it privately is because i want to do it by the end of 2016 and not when i have all my exams at the end of year year 11 in june 2017 and i have heard that private centres who do this can only do it in june 2017 which is something i cant do. Can some one tell me if it would be possible to just find a past paper online and do it under exam conditions or is this not allowed? btw i dont mind paying to do the gcse privately the problem is the time in which you have sit the exam

so you cant put it on your CV? to jobs and unis?

I'm confused, the question you've asked is if you can do a GCSE at home to which I've answered is not possible. However your OP doesn't match the question. Do you mean a mock paper or an actual exam?