If I fail in B.Sc final year & take admission in a Diploma from another university, can I give my final year exam again with Diploma exam?

Legally at a single time, you are not allowed to study two different courses. But if you want to give your exam, you can if you are able to manage both. But you can't show your both marksheets combined. So my personal opinion is that u should choose single stream and achieve peak level in that field