That's entirely up to you
in what game of Pokemon
FAP
You find him in meteor cave after beating the elite four.
Beat them and the champion
hacks. and pokemon that are able to evolve with the dusk stone won't until you get the new pokedex (after beating the elite four)
Prof oak after beating the elite four.
At 'N's Castle after beating the Elite Four.
by beating the Elite four. no i TRIED THAT ass
Yes.
You can go there after beating the elite four.
pickachoo
Typically, Pokemon Liquid Crystal should not freeze after beating the Elite Four. You may need to restart your system before you fight them next time.