i have not yet stared my preparation for iit. is it possible for an average student to get into iit at this moment of passing first 4 months of class 11

Definitely, where there is will there is a way.
Average is just a word for you till you start studying.
Make proper time table Prepare under proper Guidance.
Go through the blog I have shared
http://www.askiitians.com/iit-jee/how-to-prepare-for-iit-jee.html

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