Can someone pls guide on how tax deduction work in TCS . Because inspite for raising ticket TCS is not providing clear answers. Why org proactively deduct tax from salary let individual fill ITR and get it tax deducted .

The process is different here... You can declare your tax exemptions on a monthly basis. Whatever amount is applicable till that date, will only be considered for tax exemption.
Example: I pay monthly rs 2000 in PPF account. If I submit tax exemption request in August, it will consider only Rs 2000 X 5 (Apr - Aug = 5 months) for tax exemption. Similarly, ELSS, LIC etc some things are to be filled quarterly if you have opted for monthly payment system