Hello Narayan !!
code 2 is for the candidates who have completed their 12th equivalent to 10+2 higher/senior secondary examination(CBSE).

Code 3 is for the candidates who have completed their intermediate /12th from a board or recognised college with physics,chemistry ,biology and english as main subject.For detailed information about this NEET qualification cades just go through the link provided below:

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

Hope that helped !!

Good luck!!