Airlines - Cargo

What happens to the cargo of cancelled flight?

Cargo either will be rebooked on next flight or if customer wants to take it back,

Can do it by taking customs aproval

Why should long drive cargo be avoided?

Due to transit time. Will take long duration to reach destination.

How would you decide max.qty of cargo which can be loaded in a compartment?Depends upon the compatibility door dimension of the aircraft

Cargo flight timings between Dubai and Trivandrum

Did you mean flights from DXB to TVM.
Several flights operating . EK / FZ ,6E,Air india express