Hello Harish, 

If you are of general caste then you will not be able to give the JEE paper because the eligibility criteria for class 12 of general caste is 75% and for other caste is 65%. So if you are of general caste then their is no need for droping. You can go for other exam like:VITEE, SRM, WBJEE, COMEDK etc.

Thank you

since its matter of your career so the best guidance for you is depends on your preparation i must say if you give your 100% in preparation consistent and focused than you will crack jee mains atleast because after 12th generally we dont want to study previous concept again its human nature so 2 years is more generally max. students drop for 1 years condition they have prepered earlier some how and chances for advance are less but for jee can be 3 so its all about your determination may be in 1 or 2 year 

good luck bro any query further ask my friend