>>530526693
I don't think there was a reason given, though some people have joked that Eggman is Cream's father and Advance 2 was just some custody battle he had with Vanilla.
>>530527093
Battle was weirdly written because it released earlier than Heroes and was based on earlier drafts where Gamma and Chaos appeared, which is why Omega is only mentioned in one line of dialogue by Rouge. Cream may prefer not to fight, but she basically has an attack animal to do the fighting for her. Her character development in Battle was about overcoming her aversion to fighting. Which makes no sense since she's already proven to be capable, but maybe you can excuse it when you realize her problems may stem from Amy nearly killing herself in training.