Surf west of Cherrygrove, use rock climb and headbutt the trees. Catch it.
Level 23. 
You can't catch a Taillow in Pokemon Platinum, but you could catch the later evolution (Swellow) using Poke Radar on Route 213, and then breed it to get a Taillow.
No, you cannot catch Kyogre in "Pokémon SoulSilver."
You can't catch bastiodon in Pokemon soulsilver.
No, you can not catch Phanpy in SoulSilver. It is a version exclusive to HeartGold.
You cannot catch Heatran in Pokémon SoulSilver, you will have to trade for it.
catch it? no.
You need to breed a Male Chatot with a Femal Swellow to have an egg
You can catch him in Soulsilver but he moves around.
you can only catch him in soulsilver
any tree in cherrygrove city if you have gotten the national pokedex