I am a Idaho resident, if I purchase a non-resident deer tag on or after August 28, will it be valid for both the whitetail seasons and the regular deer tag seasons?

Answer:

You must purchase the type of deer tag you want.  If you want to hunt for white-tailed and mule deer,  purchase a regular deer tag, which is valid for either one (as long as the unit you are hunting is open for both).  If you only want to hunt for white-tailed deer in one of the later seasons, purchase a white-tailed deer tag.