Hello, hope you are doing well, yes you have good chances to get Mechanical seat in NIT in CALICUT with your percentile of 85% as well your reserved category will also help you in getting a seat in NIT. So apply for counselling, but I can not assure you that you can get computer science as it is of highly selected one and requires more than 95 % to get into it, if possible once try for it as well. To know more about the admissions through jee mains, go through the below link

https://engineering.careers360.com/jee-main-college-predictor

I think it helps you!!!

Keep Smiling:)

Wish you good luck!:)