Below is a link to a playlist that I've recorded.
It contains ALL world 2 and world 3 levels (apart from 70 and 74), on 3 stars, using NO BOOSTS!
(I Just have levels 70 and 74 left to do, which I'll add as soon as I get 3 stars on them, If I can).
https://www.youtube.com/playlist?list=PLdmC1VwRj068TssA-kX1D...Some of these levels will take a LOT of retries to do. Most of the time you will be doing well and then the game decides to give you completely useless colours...
Hope these videos help some of you out, even if it just shows that most of them ARE possible without paying.
I didn't do the 1st world as I got 3 stars on most of them 1st try, so it seemed a bit pointless.
To get 240 stars you can go past level 80 and the stars add to the total, otherwise you need 3 stars on every level upto 80.