Dear Bhanudas

According to this year's NEET brochure, it should be CODE-5 as you mentioned that you are in first year doing B.Sc. 

But you should check NEET2020's brochure in case of any changes before applying.

As CODE-5 is defined for the candidates who are studying in the first year of the three years’ degree course of a recognized University with PCB (that includes practical tests in the given subjects) provided the examination is a University Examination. The candidate also passed their earlier qualifying examination with Physics, Chemistry, and Biology/Biotechnology with English at a level not less than a core course. 

And yes, you can give NEET 2020 but make sure you have completed age of 17 years at the time of admission or will complete that age on or before 31st December of the year of his/her admission to the 1st year MBBS/BDS Course.