Hello!

So,If you don’t get a seat in the 3rd phase of TS EAPCET counselling you cannot go back to the seat you were allotted in the 2nd phase. Once you participate in a new phase of counselling and get a new seat your previous seat will be cancelled. The second round seat will be forfeited.

If you are satisfied with your seat in the second round than it's better to not participate in the next round unless you are confident that you will get a better seat in next round than you can participate it's upto you.Also read the counselling guidelines properly.