There’s is no static design to modern Sonic , he has slight changes to his model color and proportions in every story.
Sonic 06 really long quills narrow long corneas. Thin long arms and legs.
Sonic Heroes: massive feet, with huge hands that dragged to the ground. Neon loud color palette.
Sonic Forces his quills were small and he had more realistic details like scratches on his shoes and 3dish quills, and skin that realistically absorbed light.
Sonic Adventure 2 dark fur and skin really massive brow muscles. Soap Shoes.
Sonic X only three quills. Bigger head.
Sonic Prime his mouth actually was in the middle of his head instead of on the side.
Along with lesser ear and brow detail.
And triangle patterns to represent quills.
Sonic Boom taller stature, athletic tape everywhere extra quills. The rest is obvious.
I don’t know why they keep on bringing back that circa 2000 render of him but the whole point of his series is to be different in each iteration.
After all the designer of him said that he’s supposed to be make believe character that someone made as a way to tell many different stories.