Kingdom Hearts A Hypothetical & A Battle Question

First Scenario
Hypothetically speaking, what if Sora were to keep fighting the heartless on Destiny Islands until he reached level 99? I'm going on a trip and I plan on playing on the PS2 for a long time.

What would exactly happen to Sora if he were to become super strong fighting weak heartless at the very beginning of the game? I'm talking about the original KH without skip scenes.

First Question
How does one the Ice Titan? I've looked this up online and there are two ways to defeat him: have your guard up & wait to deflect his attacks or keep hitting him with fire. I've tried both of these, should I be do a combination of some sort?

Thank you for taking the time to answer my question & my scenario. I really appreciate it!

 

Yes, you can be super overpowered for the whole game. I once stayed on Destiny Islands for a while just fighting Selphie, Tidus, and Wakka to gain experience. It just makes the rest of the game a bit easier.

I also modded a save once to get me at max level from the start. It made boss fights go by pretty damn quickly.

Whatever works for you really. I find deflecting the ice easiest, especially because your MP eventually runs out.