I've heard it's so easy to earn micro-ILC by just passing any levels of the game starting from level 1. I also would like to know how much is that ilc rewards per level.
Yep you are correct and afaik you would receive 1 ilc for every 10 level you've passed. So if my computation was right we would get 1/10 ilc per level passed.
Would you know if it's possible to withdraw the earned ilcoins through the game or can they only be used exclusively within the game itself?