Anjani by mock counselling you can go through the whole procedure of seat allotment in the colleges and this mock counselling also gives you a rough idea about which stream you can get in which college so that later during the final process you can select the colleges with the stream in which you have the highest probability of getting admission. The mock counselling will also give a detailed insight on how the answers will be evaluated online.

I would highly recommend you to attend the mock counselling as it results in the chance of error to almost zero percent in the final counselling time and you are able to make your stream and college decision in a much better way. 

Mock Counselling is not necessary and have different centres which you can check on the official website.

Feel free to ask if you have any more queries. All the best!!