Hello,
you can change it during your counselling process. You can't change that now. During counselling , the persons those who will check your documents, you will have to  say them that you made a mistake during registration. They will correct it.

and about the government college , you may get  but chances are low as you rank is high.

any way try looking for one which will be suitable for you.

• Dr. Ram Manohar Lohia avadh University
  

you can try for this college you will get it as your rank is in the range.

you can use the  UPSEE college predictor:-  https://www.careers360.com/upsee-college-predictor

Hope it helps!