Answer 1

The XPs for Challenges are calculated as below:
Just getting started : Win a challenge
20 XPs

On your way to fame : Flawless victory in a challenge 
50 XPs

Rising Star : Win 5 challenges in a row using one weapon 
100 XPs

Challenge Master ; 5 flawless victories in a row using one weapon 
100 XPs

Unbeatable : Win 10 challenges in a row using one weapon 
200 XPs

Gaining Experience : Complete 50 challenges using one weapon 
100 XPs

Master : Win 50 challenges using one weapon 
100 XPs

Epic : Win 50 challenges in a row using one weapon 
500 XPs

The Player : Complete 100 challenges using one weapon 
200 XPs

Unstoppable : Win 100 challenges using one weapon 
200 XPs

Practice makes perfect : Win 200 challenges using one weapon 
350 XPs

Respect : Complete 500 challenges using one weapon 
400 XPs

Guru : Win 500 challenges using one weapon 
500 XPs