The question you have asked, in such a manner that what you want to know is hard to understand. Now I guess you are asking that you have done your Madhyamik on 2013 and on 2015 August you have applied for the Diploma and you are asking that you are eligible for the TCS or not.

See TCS don't impose any such eligibility conditions regarding drops or the gap years. So for that matter you won't face much of a problem. But you must be sure that you are satisfying the other criterions such as the Skills required, Marks in your Diploma, Age etc. Due to the GAP year you have nothing to worry about.

Have a great day!