Raikou is not in Pokemon Diamond. Are you using an action replay or a game card that may have been altered? Did you mean raikou (4 legs) or raichu(evolution of pikachu)? How did it appear?
no because if that happened it must have been a glitch
yes of course,there are two option,seek until you have one or use the pokéradar
Oak's lab isn't in Pokemon diamond unless it's hidden. But you might be able to use action replay to make it appear. Hope i could help! Sorry the font changed.
NO
Shaymin is an event Pokemon in diamond, pearl and platinum to get it you need oaks letter then he will appear on some route apparently if you talk to him and show him a Pokemon that likes you a bridge will appear and will lead to shaymin.
Alamos Town does not appear in the Pokemon Diamond version of this game. It is in the movie, but not on this game.
Repels make WEAK not strong Pokemon not appear
I don't know what you're exactly asking, but if you mean by all Pokemon that appear in the wild without the action replay in, then no, but if you already caught, then yes.
So far, the only codes to change a Pokemon's ability are Pokesav generated. Codes such as making a shiny rayquaza appear in box 18 with the ability intimidate.
below 50%
You do not have to fish to get Krabby in Pokemon Diamond. However you do need the National Pokedex to make Krabby swarms appear.