In What way Prepation of IITJEE and boards different? If I preapre with focus only for boards,do i stand a chance in IITJEE and vice versa?

Although syllabus for Boards and IITJEE is very similar , In IITJEE clarity of concepts and thinking ability is getting tested while boards tests the understanding of basic knowledge of subject. Just preparing for boards may not equip you for sound application of fundamentals and ability to crack questions with multiple concepts. However, preparing for competitive exams focus to understand subject at a deeper level and hence directly contribute to preparation of boards. However, many practice tests on board level should be taken with proper test analysis to ensure proper understanding of pattern and marking scheme. Preparing with only board exams in mind may not give you edge in competitive examinations.