Suppose, you have a virtual card allocated to you but you are not using it and want to pass it on to another user who will be taking care of ongoing expenses and ideally needs a card. Is there any way to reallocating a card?

The answer to this No, this is not possible. There is no way you can reallocate one person's virtual card to another. You have to block the virtual card and create a new virtual card for the new user.