Hii

Final year appearing students are also eligible for CAT exam, But if they got selected, they need to provide the final result before admission processs. Otherwise there candidature might be cancelled.
Also a few colleges have an option of Provisional admission, where you need to sign an undertaking that you fulfil all the eligiblity criteria and that once the results are declared, you will provide an original copy to the authorities for the purpose of checking.
And that if at any stage you eligibility is not matching the required criteria, your admission can be cancelled.
So if you are in final year you can appear for CAT, but admission will be basis on the fullfilment of all the eligiblity criteria.

Hope this helps
Thanks!