You have the right to get migration certificate from the current college if you get admission in MBBS via NEET. Any students who pass 12 with PCB as main subject can attempt neet at age below 25 are eligible . It is not necessary to finish your Bsc course. Large number of students do the same thing, they also admit to different course like agriculture or zoology and prepare for NEET at the same time. If you clear the exam and secure a seat then you drop the Bsc course.