Hi
One needs to understand that the word CTC is a cosmetic figure to show the company in a better position towards the employees than they actually are. It is basically Cost to the Company which should in no way be treated as same as Gross Salary of the employee. Only when they show under the term Gross Salary of the employee you can take the fight to the employer's court else NO.
As far as the Payment of Gratuity Act, 1972 is concerned it is quite clear that one has to complete full 5 years to stake a claim for Gratuity, as rightly pointed out.
Thanks and Regards