In Pokemon Crystal, how do you get the Tm Dig? And Espeon and Umbreon and Lefeon and Glaceon?

I know it’s found outside of the National Park, but I can’t seem to go there. The item ball is surrounded by the fence and I walked around the whole thing to try to find an exit. Going outside through the house won’t work either: then the item ball is nowhere to be found.

Can I evolve a eevee into those four in CRYSTAL or is it only possible in diamond and pearl?
And one more question :Where do you get strength?

if its the same as silver the fence has a boken piece up at the top sorta and it will make its way down there it took me forever to find that spot and glaceon and leafeon cannot become a pokemon on crystal but espeon can