Hello Ashwani,

No you will not have to register again, you let the seat that you got in Round-1 float so there now you will be considered in Round-2, however you will have to forfeit the security money you paid for Round-1.

Although the registration begins again before Round-1 but that is for the students who missed to register the first time before Round-1.

Hope this helps.

Hello,
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Yes,you need to apply for 2nd counseling.
But don't be in a expectation that you will get a seat in the same college.
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There are very less chances to get a seat  in the same college but you will get a seat in some or other college for sure without any problem.
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If you want a seat in the same college then Give a try by visiting college and inform them that this happened,ask them will they provide you a seat in 2nd counseling.
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Best of luck