Can I stain a piece of wood first to a color of choice and then finish with Tung oil? Also does Tung oil need a protective finish coat when the final coat is on and dry?
Any oil based wood stain can be applied before finishing with several coats of Tung Oil. Allow the stain to fully dry overnight and apply thin coats of Tung Oil, typically 2-3 applications of Tung Oil is enough. (Take a look at <a href="https://www.house-painting-info.com/tung-oil-finish.html">Applying Tung Oil</a> for more information.)
Tung Oil doesn't require a protective coating after application. It is the actual protective finish that is applied over the stain.