Thanks for your questions.. Buddy sliding round is basically second part of the third counselling.  To keep it simple you can take it as fourth round of ipu counselling.. The college seat which you receive in sliding round after the third round will either get upgraded or will be retained.. So you don't have to worry about that.. .but if you wish to apply for even better college you can go for spot counselling. .athough it is riskier ... Anyways All the best