A few questions about pokeballs...

[Kikyo]

I think the inside is like a little home that's modified to the likings of the pokemon inside it.

As to how they know, I think they simply memorize the order. One of the trainers in the show had to put a different sticker on each ball to memorize them.

[Umbreon Master]

Its probaly a small world made for one pokemon, with its own liveing room, kitchen, t.v and a supplly of K.F.C LOL! Nah its probaly something like the pokemons habitat. Trainers probaly know witch pokemon is witch pokeball by heart.