/train/6031and
/train/7943/6798/7037 are BR trains and has Indonesian made Coaches (BR's Best coaches. some what our LHB Counterpart)
while
/train/6935 and
/train/7944/6798/7037 are IR trains hand has Conventional ICF Coaches.
However Loco links are same for All four. KOAA-Darsha(BD)and Darshana(BD)-KOAA : BWN WDM 2/3A and Darshana-Dhaka/Dhaka-Darshana-Iswardi WDM2 . it is a 6 coach train, Just!