There is no Pokemon called Leo
A swarm
You can catch as much as you want.
AR/Event
i would say starly, bidoof or shinx
you can catch in in ruby sapphire emrald pokemon dp platinum and pokemon black and white but groudon exists in ruby and emrald.kroge exisists in sapphire only
You can use a cheat, or Nintendo WFC, but you cant catch it in diamond or pearl.
You cannot catch slowking you must catch a slowpoke give it a king's rock and trade it. If you have more evolution questions or you need to find out where to get a certain Pokemon I suggest going to www.serebii.net and clicking on dp pokedex.
In Celestic Town with a Super Rod http://serebii.net/pokedex-dp/342.shtml
go to this link it gives you details on every Pokemon and where to catch them if possible http://www.serebii.net/pokedex-dp/037.shtml you can change the dp to rs for details for the ruby/sapphire version of the Pokemon if the Pokemon appeared in ruby/sapphire or before
there are three shows and a lot of movies Pokemon dp Pokemon dp battle dimension and Pokemon dp galactic battles
well i don't really now if you can get aerodactyl in Pokemon dp or you could try
To get a Giratina in Pokemon Diamond, you'll have to catch it in Pokemon Platinum, then trade it to Diamond. However, when you catch it in its Origin Forme and trade it to D/P, it'll revert back to its original form, due to Pokemon DP not having the Giratina Origin Forme sprite programmed into the game.