DP with Bitmasks : Travelling Salesman Problem(2-D DP)

#1

Here in the example shown in the video there was no overlapping subproblems in the recursion tree----then why we have used the Top Down DP?

#2

suppose u know the ans from city 1 to city 2 to city 3 and after that if at some time you start from city2 to city1 to city 3 then this answer was stored already in dp.