sir,currently I am in first year of nit patna.I passed my class 12 in 2012.now I have one more attempt of jee mains.I want to use that attempt to get into some better nit or iiit. So sir please tell me if I score well in jee main 2014 will I be able to go to some other nit. Also tell that does 2 year gap after 12 matters in b.tech

You mean you already in NIT Patna yet planning to move to better NIT or IIT ..
I will never recommend that because it will be then waste of one precious year , I suggest you to finish you studies here and if you are academically strong, you will definitely get bright future even from NIT Patna.

Good luck and God Bless You!