If you have BSc PCB then you can apply for the code 5 or code6. But as you didn't have PCB combination in your BS then you can't apply for it.

Thus if you wish to apply for NEET then you have to use the code 2 which is for droppers.

The code 2 is for those students:

• Completed 12 years of school education from CBSE/ICSE or any other boards with the last 2 years having the subjects English, Physics, Chemistry, Biology/Biotechnology, or Mathematics or any other elective as a major subject .
• Students who have passed from NIOS/other open schooling board with Biology/Biotechnology as one of the subject in 10+2.
• For the droppers.

To know more about NEET 2021 qualification visit the link below:

https://medicine.careers360.com/articles/neet-qualification-codes

I hope this answer helps. All the very best for your future endeavors!