Who won least number of matches?

Amit own maximum number of matches.

B and E

E and F

B, E and F

D and F

Amit and Gandhi

3

Hemant lost to both Firoz and Gandhi.

If a player eliminated in 1st stage even after scoring maximum possible point the it is possible when top 5 has same points and Rajesh got eliminated with tie breaker rule. In this case bottom three got points because of matches between them.
Out of 56 matches there are 6 matches played among bottom three hence total points in remaining 56 - 6 = 50 matches is 50 x 3 = 150 that is equally divided among top 5 players equally i.e 30 points each, So Rajesh can not get advanced even after getting 30 points.

In this case top 3 players should get maximum possible points and remaining 5 should get equal points and Rajesh got advanced with tie breaker rule.
Bottom 5 player have in total 4 x 5 = 20 matches and each match will fetch minimum possible points when its result is tie. So minimum points in 20 matches is 20 x 2 = 40 when distributed equally to bottom 5 each of them will get 40/5 = 8 points.