Problem deleting a game and starting over

I use an iPad 4, and am kinda new to this stuff, so let me shoot out my question here :

I recently installed the game "Hero Hunt" by Grey Area Labs, and since i made some mess ups in it, i am unable to continue playing it further, and i reached the point where i have to delete it and start it over, but am unable to do this since Game Centre keeps tracks of my progress in the game, and even if i re-install it, i continue from where i left off. I tried changing my Game Centre account too, but even if i install the game on a new different Game Centre account, the game still recognizes my old content (Is the game info stored on my iPad ? ) So is there any way that i can access the game from the starting ? Any help would be greatly appreciated. Cheers!