You can find Jolteons at Spacial Rift.
You can find recruitable Gastly and its evolutions in Sky Stairway.
anywhere
You have to buy it in a shop
You find a chimchar, train it, evolve it.
Find them all.
you find darkrai in the dark crater!
No. You'll have to find some more codes specifically for explorers of sky. (Sorry I don't know any. I only have Time and Darkness.)
i do not have explorers of sky
in any dungeon
yes
Arceus, as a living entity, does not appear in Explorers of Sky. There is, however, a statue of Arceus on the 99th floor of Destiny Tower.
spacial rift