I'm unable to access world 3. I've already completed worlds 1 and 2 on easy, medium, and hard, all with 3 stars, but world 3 won't release for play. What should I do to continue the game?

I've completed levels 1-14 with 3 stars on easy, normal and hard but I simply cannot survive level 15. Any tips?

Was in Groupees Casual Bundle 4

Are there any shortcut keys for this game? Eg. for pause/unpause, next wave, speed up/down, cast spells.

I have now 100% of the achievements, but i have only 89 of 720 possible Stars yet and have not completed the first of 4 campagnes. 60% of the achievements are possible in the first 5 missions. 4 achievements are possible to get directly easy at the first mission when first playing it. Is it planned to implement a few harder achievements?...