hi kuldeep,

i dont think you can participate in mop up round since you have already been allotted a college in the second round. mop up round for those students who haven't been allotted a college in any of the rounds before. so ,sorry but you can't. 

Hii aspirant ,

Coming to your question I would like to tell you that as you have mentioned that you got a college in the second round then also you can participate in the mop up round ,

Hope this helps you,

Good luck.