Sonic the Hedgehog: Return to Soleanna

Dr. Eggman has gotten his hands on some blueprints for an invention that can change Sonic & the gang's lives forever; a genetic alternator. Along with their new forms, it seems that they've been transported to a place they haven't seen in 4 years, Soleanna. Can they get home to their original forms; or is a reunion with a certain Princess distracting Sonic from the mission at hand?