its very hard to complete all 6 levels unless your willing to use boosters. you can learn the lower tiers easy but as soon as you get to 4,5 and 6 then unless your extremely lucky you will need to use boosters.
Yeah, this event was not easy as I did. Extremely impossible if completed all 6 levels without boosters. But reward from this event is absolutely amazing. I want it but I give up to complete this event. So, I lost them all...
Oh, you can get 2 of each boosters (Swedish fish, lollipop hammer, free switch, and color bomb, if I'm not wrong) by passing all 6 levels in a row, but you need extra effort to pass all levels and of course, luck.