Hello aspirant  , hope you are doing good.

So, to answer your question, Yes , you can definitely get a seat in further rounds if your rank is good enough, without even getting a seat in mock round. The mock round is just a test round, and it's not really an actual round of counseling and that's why the term 'mock', so it's result are not very important. Infact, if you don't get a seat in 1st round as well, you can still be hopeful for the 2nd and 3rd rounds of counseling.

Hope this helps you. GoodLuck !!