You can't get Dark Lugia in Pokemon Silver, Gold, or Crystal. You can get Dark Lugia in Pokemon XD though. For Pokemon Silver, Gold, and Crystal it is just the regular Lugia.
In Dark Cave.
Geodude, Dunsparce, Zubat and some water pokemon.
You can find it in the Dark Cave.
Yes by trading.
There are none. Dark Pokemon were first introduced in Gold and Silver with Umbreon.
It can't get dark.
probebly dark pulse
Route 31, outside of violet city.
Wobbuffet can be found at Dark Cave, which is at the entrance of Route 45.
Houndour was a Pokemon released in Generation III. Pokemon Gold is a Generation II game. Houndoor was not introduced at that time. Therefore, you cannot get Houndour in Pokemon Gold.
In Gold and Silver Wobbuffet can be found in Dark Cave. In Crystal, in addition to Dark Cave, you can also get one at the Goldenrod Game Corner for 1500 coins.