Hello 

Yes, you can change the sequence of your choices as well as edit or add more choices to it. The changes in choice filling can be done till 12th July only. Try to fill maximum choices and always keep the best colleges first. 
But after 2nd counselling, changes in choices can't b done, so please fill in your choices carefully.

They must have recorded all the details.
A/c to my knowledge they do not allow change after this