Yes , if you want to apply under pmsss scheme you have to cancel your current admission if you are alloted a college and you want to take admission in that college And have to start fresh from the first year in the new college alloted under pmsss scheme .
If you want to participate in counselling no need to cancel , you have to cancel if your admission is confirmed in the college alloted by pmsss as because the college will ask for the education gap and migration certificate that you get after passing 12 th standard .
Please revert back if you have more doubts .