Hello kid,
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First point is yes, you can leave the course with or without informing. That may or may not bring impact in your life but, according to me firstly inform in your college about NEET examination. Look most of the college's do give students a choice of rejoining if they want to after giving national level examination and cancel their admission if they don't want to join.
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So now, if your College is going on then inform them about about examination you are giving, it's not mandatory but ask them, how can you leave the college in middle if you get a seat in MBBS. So, here they will let you know the procedure of discontinuing and you can make the documents ready immediately if you get a seat in NEET.
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So, yes you can discontinue but do inform in the College and take their advices

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