Hello student,
It's very difficult to predict the exact possibilities of admission, as it depends upon the cut-off marks. Cut-off changes every year. It depends upon a lot of factors such as the exam difficulty level, the number of students appeared, the number of students qualified, the highest NEET score and whether you belong to any category or not. Cutoff changes from state to state. It also differs from state quota seats to all india quota seats.
Here you haven't mentioned your state and the category you belong to. So it's quite difficult to predict the exact possibilities. However, considering you as a general candidate, with 491 marks the chances of getting a government seat in government medical College seems low, as you need to score atleast above 550 to secure a seat in government medical Colleges under general category, however you can get government dental colleges.
To get an idea about which college you might get you can check the NEET predictor tool mentioned below
https://medicine.careers360.com/neet-college-predictor?icn=QnA&ici=qna_answer
https://medicine.careers360.com/articles/neet-rank-predictor
https://medicine.careers360.com/articles/neet-cut-off-for-government-colleges
Hope it helps.
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