No definitely not if you have some knowledge about it then it is good bt even if you don't have any knowledge it is also good. You will get proper chance to learn it in the college . It is also included in your btech syllabus. Do you remember any incident from your school life where you have read a chapter before it was taught and next day when you teacher teach that lesson you feel confident . It is just like that if you know it then you will become quite confident and if you don't know you will learn it from basics. Dont take so much tension about it .

No it is not like that .
After joining CSE you can be a good programmer so in CSE programming is needed after completion of course but not before that .you can learn the coding easily as per your practice after the admission .
As much as you program that much you will be a good programmer .

No, It is complementary to join CSE branch with having skills beforehand. You will eventually get to know about them and you will get your hands onto them according to your interest. 

Also CSE not just comprise of Programming languanges but alot of more subjects.

I am also a CSE student and I did not have knowledge about them in the start but eventually I got my hands on them.