During dvadasi should we partake the salt less paranai without touching the teeth? I have heard vaguely in my younger age that one has to take three morsels of it, kindly clarify.

During paranai, sundakai and agathi keerai are to be taken salt less, but there is no rule that it has to be taken without touching the teeth. There are no such restrictions that it has to be three morsels. Both sundakai and agathi keerai have to be eaten before partaking the cooked food. As some might just eat only a leaf of agathi keerai and leave the rest, you might have heard three morsels in terms of inducing to eat more rather than a rule.