Can I can prepare for both medical and engineering for this which subjects I have to choose for10+2
Don't go for both the fields.Choose only one of them as it may affect your near future.
However yes you can go for both fields if you choose PCMB group in class 11th admissions.
Good luck.
Subjects needed for that are
Physics
Chemistry
Maths
Biology
But choose only one line either engineering or medical and prepare well for what you choose.