Will dropping two years for the JEE and getting in NIT Jamshedpur (CSE) affect my placements?

The majority of the companies will not pay attention to your gap years; instead, they will look at your abilities, strengths, and potential. Placements are more about what and how you fare in the four years of your engineering rather than what you did before that.

• Some of the primary things that most of the top companies lookout for are communication, skills, potential, knowledge of your subject, technical know-how, and your approach towards the work. You should start paying attention and working towards all these factors.
• You should try to focus and work on the things which are in your control rather than worrying about things that are not in your control. 
• If you have exceptional skills, prove your potential and passion to the recruiter, have the capacity to stay focused under all types of situations.
• If you feel you are lacking in any particular area, you will have ample time to work on that prior to your recruitment process. 

Make the best of this time available to you, take help and guidance from your mentors, speak to your seniors and learn from their experience and there should be no stopping you.