Dear Rupeshdelhi,
Simply being terminated by the company is no reason for denial of gratuity. Even termination for misconduct is also not a reason, as there are many misconducts which are not considered serious or warrant major punishment like termination. Additionally, the company has to prove the misconduct through a proper inquiry that adheres to the principles of natural justice. Moreover, the inquiry has to be quasi-judicial in nature, something that very few companies have the know-how to conduct.
From my experience, I can tell you that the company shall be forced to give you gratuity if the matter goes to court (assuming other things are as true as stated by you). The fact that ex-employees do not fight for their rights encourages these companies to be arrogant enough to violate laws.
Warm regards.