Is all sweet corn hybrid

No, sweet corn varieties were first grown by Native Americans. Now a days most of these varieties have been lost and hybrid varieties are the most common. You can still find older varieties at places like Seed Savers and Johnny's Selected Seeds. Country Gentleman and Stowell's Evergreen are two of the more common, though others are available, particularly from "heirloom" seed houses.

GMO, or genetically-modified organism, corn is not available to the home gardener due to the proprietary legal requirements attached to the use of the seed.