All old Pokémon exist in the games, but it's a question of whether they'll be obtainable ingame, since some older Pokémon in other games have to be transferred into the newer ones. So there will be a fair amount I'd say, but you'd probably have to trade for a lot as well.
Yesterday I accidentally swallowed some food coloring. The doctor says I'm OK, but I feel like I've dyed a little inside.
No idea. A few have been shown to, but there's no confirmation of if the entire Gen 1 pokedex will be available in either game. Most likely we'll need to trade, transfer them from older games or use some other software.
Playing) Fire Emblem: Awakening, Guild Wars 2 Waiting) Pokemon XY