Super Sonic is a faster and stronger form of Sonic, increasing both his speed and power by 1000%. He is also given the ability to fly and perform some of his own unique attacks. When it comes to a large monster or you know, the final boss, Super Sonic is most likely to come into play. What makes him do this? The Chaos Emeralds, why did you even ask that, I thought you knew what a
was. He needs seven of these to activate this form, and can even summon them at will like it was an emergency-only situation.
In this form, he is immune to damage, but that doesn't mean he has no limits. First of all, he can't keep it forever. The longest he has kept this form was about a week in Sonic Advance. Also, he can still run into obstacles that stop his progress for a moment. Finally, he can even lose his form if there is such a force to do it, such as atmospheric reentry because it happened twice. Once to Sonic, and the other to Shadow. But that doesn't happen much, so let us not worry about it right now.
...What? Rings? That's just a game mechanic. If Super Sonic was kept for a week in Advance, just imagine how many rings Sonic has kept. And what if you just lost rings before it even happened? It's just like Golden Tanooki Mario being able to OHKO enemies that are made of lava, but dies when touching lava as a hazard.