Already a Junior now. Should I change my major as a new freshman or transfer student?

Hi,

Im in an undergraduate program in China and came to Columbia as a visiting student. I was pressured in to finance major and I hoped the education here would let me forget about my favorite subject, biology. But I still love biology and science and want to follow my passion. So Im considering a change.

Could you please tell me if I could apply for freshman somewhere? I really would like to have a new start in the states.
Also, do you know which option has better chance of a scholarship?

Your help would be much appreciated!