Gratuity - management had extended my service

I attained superannuation in 2014 as CEO of a Co-operative Bank after putting in service of 18 years. I received my gratuity from LIC in 2014. However management had extended my service till 2017 year by year without any break and with all benefits as permanent staff i.e. P.F., exgratia, leave, LTC etc on the same wages and allowances with increment on account of wage revision of staff during the period of this three years.
Am I entitled for gratuity for 21 years instead of 18 years (already paid) on retirement in 2017?

If they have cleared all your dues & completed full and final settlement in this case you may not be able to ask for Gratuity for 03 extended years as LIC has to be intimated in advance while taking group gratuity scheme for Retirement Age & any gratuity claim will not be entertained after Retirement Age.

Has management extended your service with continuity in Service.What are the contents of Extension Letter? if your service was continued, how your Gratuity was settled while in service? Please provide all details for clarity in the matter