It seems that you have joined the company in 1990 and was enrolled under ESI & PF 3 years later and your date of superannuation is in 2020. In the meantime it appears that the company has submitted a letter before DLC, Barrackpur declaring closer in 2012. However, as per the said letter, your employment was untouched. In this situation, there is no harm in claiming the gratuity after your superannuation.
You have to send Form I to the company after your superannuation and wait for 1 month.
If they do not pay, you have to make an application in Form N before the Authority appointed under the Payment of Gratuity Act, which is mostly at the Asst. Labour Commissioners.