My Concern here
Can i fight legally to claim my property right? As this property neither belong to my father nor my grand father and purely my grand mother!!!
This property belonged to your grandmother hence she has rightly bequeathed the same to the beneficiaries as recited in the Will. The will being a registered will, cannot be disputed about its validity. When the Will came into force, your father was a minor and naturally the property was under the care of his natural guardian by an arrangement within the family, but in no way authorised your grandfather to mortgage the property belonging to the minor son (whether for the purpose of business r anything), so basically assigning the property to bank for loan purpose on mortgage was illegal and invalid in the eyes of law.
Further your father has only life interest in the property to receive the revenue from it and not authorised to mortgage the property for loan purpose, therefore in any manner it is illegal and no binding on the end beneficiary, i.e., you.
If so what is the right approach to fix the problem? Can i claim that my father and bank have cheated me and misused my property to get back?
The question is not about cheating you but you have to reclaim the property on the basis of your entitlement made as bequest in the registered will and can obtain an injunction also on the same lines.
What are odds that i could win this case?
You have merits in your side, if fought well, you can easily win the case.
Is it time taking process?
Yes.