After my 12th I joined another course for 1 year so do I need gap certificate to take addmission in 1st year???
Nope if you have take admission in any other college and if you want to switch college as well as to take admission in another course then you have to apply for the cancellation of your admission at that college and then you can take admission in that college. Also some colleges may ask you for Transfer certificates issued by your present college principal.
Now if the college you want to take admission in ask you about this gap certificate then its a different issue. But its very unusual for any college to ask about such documents.
I hope this answer helps. All the very best for your future endeavors!