Hello

Yes if you have not booked any seat in the first round this means that you want to go for the second round and you are eligible for the 2nd round.

If there is any seat alloted in the second round and you want to book that seat then you are not eligible for the third round, it all depends on which round you book your seat and you wont be eligible for the next round i.e no seat would be alloted to you on the nest round since you have already booked the seat.

Hope it helps.