I able to participate in 3 rd bcece counseling when register reply your current auto upgradation status is yes/no it mean
If you have been allotted a seat in any of the previous rounds (like you say in round I), you can still participate in 3rd round of counselling. But please note that today is the last date to fill fresh choices. If you are offered a higher preferred seat in 3rd round, the seat offered in the previous round will stand cancelled.
As for selection of auto-upgradation status, if you opt yes then you will automatically be considered for a higher preference seat if there is a vacancy.