4+3=9

I am an international y12 student doing EDEXCEL Physics & Maths and AQA Biology in the UK (linear). I was hoping to be able to finish them in my home country (financial/familial/personal reasons) but the only option there are IAL, the modular courses which require AS qualification. As of now I'm getting a B/A in
Physics, B/A in Maths and B in Biology. Teachers are predicting A for Math and Physics but a B for Biology. Is there a way out for me? I have studied CIE Biology in the past and I am familiar with the International papers for all the subjects but not necessarily the structure. I know that for CIE Biology I need to do practicals which can be arranged. In the future I want to apply to universities around the world for mechanical engineering. The two accredited schools I found for year 13 transfer were pleased with grade transcripts but required AS qualifications.
Does anyone know good Online accredited schools? For most universities that I wish to apply a school transcript and graduation certification is a must and that's one of the main reasons as to why sitting the exams as a private candidate is not a viable option. A very important moment- I am an early 2006 teen and cannot redo year 12 as I'd be bordering 20 if that's the case, there's no way my family would allow it either. None of the adults that I know are versed in this education system and I am very worried about the future and how I can waste money and time and effort to get subpar results. I will be grateful for any advice/experience