Easy just use a leaf stone that's it.
Shaymin does not evolve in Pokemon Diamond.
The Leaf Stone can only make 5 pokemon evolve. Gloom into Vileplume, Weepingbell into Victreebel, Exeggcute into Exeggcutor, Nuzleaf into Shiftry, and Pansage into Simisage.
yes it can evolve
you need to battle with it alot to make it happyer then it will evolve
Leave it with the nursery
you don't it;s impossible.you can make swinub evolve but not piloswine.
you don't evolve it by a stone it will evolve by levels
lvl it until it evolves
the moon stone.
U Level it up of course
With an oval stone, you can evolve Happiny into Chanssey.But, you need to make Happiny hold that stone and then level it up in order to evolve.
make rhydon hold the protecter and trade it then it will evolve