Yes. You can guess. Only issue is the negative marking. You lose 0.25 for every wrong answer. You need a strategy for answering NEET. It depends on what kind of score you are looking for. If you want 520 and if you are confident about 130 questions and are sure then guessing for the remaining questions might actually reduce your scores due to negative marking. Of course you can not be 100 sure that all your answers will right so you may have to make efforts to answer as many as you can while keeping your negative scores to a minimum.
But supposing you want 520 but are only confident about 110 questions. And not sure about the 20. So you still have 50 questions to guess and make up for your 20 questions. Here you need to be intelligent in guessing. That is if you are 100 % sure that 2 of the answers are wrong. Then you have to guess between only two alternative among 4. So you can either be right or wrong giving you 50% chance of getting it right. If you can eliminate only one alternative then your chances of getting it right fall to 33.33. So it’s all probability, playing against the odds and your luck on a the exam.
The above tips are only to try and maximize your score. Ultimately it is your hours of preparation, hard work and confidence in yourself that will help you reach your goal.
All the best.