I can't seem to find the answer to this.

So, I unlocked the new Challenges log. I did some leves on my low level Arcanist, it got an entry in the new log. I switch to my low level Conjurer, and they entries are still there. So that means it's a weekly account log. So far so good. But you get rewards for it. I haven't filled a bar yet, but what I would like to know is:

1. When you fulfill a challenge do you get the reward immediately? Or at the end of the week?
2. On which class do you get the reward? The active class?

Just would like to know for sure, since it would be a pitty to get XP rewards on my level 50 if I could have gotten them on one of my low levels.