1. No, you cannot evolve him. Nintendo wanted the game to be like the show, and since Pikachu wouldn't let Ash evolve him in the show, you can't do it in the game.
2. You have to beat Giovanni in the game corner for the Sliph Scope (or simply buy a pokedoll, but doing the training makes the rest of the game easier.) Then go to Lavander Tower and use the Pokedoll on the last Ghost (the one that won't let you access the staircase). If you have the Sliph Scope, it will automatically ID the Ghost as a Marowak, but you cannot catch it (but you can catch one in the Safari Zone). Defeat the Marowak and head upstairs to battle the Rockets and rescue Mr. Fuji to get the PokeFlute. After that, the Rocket guarding the Sliph Co building will be gone.
EDIT
Oops, forgot about number 3!
3. Ho-Oh is not in the game, as it is the 250th pokemon. Mew is the 151st pokemon, and the last one that will appear in the pokedex.
« Last edited by drewdrewrocks on Jan 3rd 2007 »RAWR! Who's the Boogie Monster NOW!!! MUHAHAHA