When you use Surf or Rock Climb.
You switch the pokemon you have in your party or you could ride your bike. I would just ride my bike if it was me.
ride your bike back and forth in new bark town
make it hitch a ride on a Pokemon from the gba games you can find one in almost all of them
no you can trade soulsilver pokemon to black
he is not in Pokemon soulsilver or Pokemon heartgold
POKEMON SOULSILVER come with a poke walker and the Soulsilver game
Pokemon soulsilver and Pokemon heartgold are basically the same game just different versions but i do recommend buying Pokemon soulsilver
You get on Pokemon Soulsilver and choose the option Connect to Pokewalker. Then, you choose Return from Scroll. To get rid of items you've acquired or Pokemon you've caught you choose Receive Gifts.
SOulsilver
You can't catch bastiodon in Pokemon soulsilver.
You CANNOT LEGALLY download Pokemon Soulsilver.
You'll need to trade for it from Pokemon HeartGold. It is not avilable in the wild in Pokemon SoulSilver.