The youngest person to circumnavigate the globe single handedly in a sailboat is currently Dutch sailor Laura Dekker, who completed her 518-day trip at the age of 16. She was sailing the Guppy, an older style and slightly modified Jeanneau Gin Fizz ketch.*
*ketch = these days cruisers called a ketch are more properly a yawl, with a larger main mast and a smaller rearward mizzen mast.
The oldest human to circumnavigate the globe is Minoru Saito of Japan, who completed his extremely difficult “wrong way around” (east to west) voyage at age 77. He did it in a custom 50’ sloop, the Shuten-dohji III.
This is what the nav station of a circumnavigator looks like (on the Guppy).