It's not bugged, Maximize Magic I is rewarded during the training, it's not something you purchase from the shop. I'll check the spell "Great Devouring" having the same text as Boreas Wrath, that might be a typo (they should still work differently, just a visual bug), as for not working, you're simply failing your casting and/or missing your enemies. It should rarely happen once you have enough magic to access those spells. Also, some enemies have magic immunity (such as Crystal Mantis).
I don't remember if Great Devouring works the same way as Earthquake, but flying enemies are immune to that.
I hate to keep bothering you, but I got the blue orb and opened the hidden room, was I supposed to eat the rotten fruit or not? I ate it and it said I had a strange power welling up and then it took me back to town with a skull in the corner, did I die or something else happen? thank you again for putting up with me.
Yeah, that's what it's supposed to happen. You pass out from it, but awake with a newly found power (which is the ability to learn up to 12 spells). There's no death in the game (aside from game over screens, which are rare). The power you unlock carries over in the sequel as well, so it's a good thing to have whether you are currently doing a magic-oriented playthrough or not.