No there are no such difference in the codes for different boards. You have to select the codes based on the category of student you are in i.e., if you are a dropper/if you have a appearing student/you have passed the graduation with PCB etc. All this cases have assigned code which you can apply for NEET registration.

To know more about the code of NEET visit the link provided below:

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

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