Hi Aspirant,

Each exam and counselling has different guidelines and conditions.If you are talking about JEE if you go for the last third round or mop up round and do not get a seat then your previous seat will be retained and at the end you have to select it without any choice.The same applies for any state level engineering entrance exams.It would be easier and accurate to answer if you would have mentioned the name of the exam.

Hope it helps!!