i m getting 400 marks in neet 2021 what are the chances and seats 0f government and what is the process

Hello aspirant
Hope you are doing well
It is difficult to predict the cut off marks or ranks but according to previous year trends your expected rank would lie between 203121 - 215020 but it may vary every year depending on the following factors
1. Level of question paper
2. Total no of candidates
3. Category of candidate
4. Total no of seats
5. Marks obtained by students
Here is the link for the expected marks vs ranks
https://medicine.careers360.com/articles/neet-result-marks-vs-rank
As your profile suggest you are from Uttar Pradesh and assuming you are from general category so it will be difficult for you to get seat in government college because for general category the cut off is around 570 above but you can get  BDS and private medical colleges
Below is the link for the previous year cut off you can visit that link to get more information about it.
https://medicine.careers360.com/articles/neet-cut-off
You can use college predictor tool too
https://medicine.careers360.com/neet-college-predictor
Good luck
Hope it helps