i went to PRS Counter to book ticket based on the assurance as per Entry 613531-7. When enquired with a couple of senior PRS clerks, they too informed me that it is not possible, since Tatkal tickets are issued on Point-to-Point (still i dont know what is that).
Anyhow went ahead and booked a CNF Tatkal ticket. Now i am planning to approach CRS soon with my request to change the BP. Still if it is not possible, i have to take a risk and hope that my berth is not allotted to others by TTE