Level 28 is beatable without the premium upgrades; you just need to lose a couple times to know when to preemptively use your spells before the shamans appear. Level 29 is most definitely impossible without the premium upgrades from my experience; can't even get remotely close.
This game came out a month or two ago. Maybe one or two slight differences, but ultimately another games8 game where they change a couple things and introduce it as a completely new game under a different title.
is unlocking outfits really the only purpose of collecting coins? Most games with stores have things you can purchase that aren't completely useless...
The whole game is definitely beatable without premium items.