Yes. In pinwheel forest down some stairs at a dead end where there is a pond. I had repel on and he showed up at level15 when my Pokemon was at 42
No you can only get him by obtaining a Oswalt in the beginning of the game, not wild...
Pinwheel forest
There are no wild Fire-type Pokemon available to catch on Route 2. The earliest you can get a Fire-type Pokemon if you didn't pick Tepig is the Dreamyard, where you're given a Pansear if you chose Oshawott.
You cant
You can't find it in the wild, but you can find a Pineco and level it up to 31.
You can find it on Victory Road when you almost get to the Pokemon League. Go down the slope on the left and you will find a poke ball, it contains wild charge. That is where you can get it.
Do you mean Thundurus? Thundurus cannot be in the wild in Pokemon Black, but you can trade for it or wait a Mystery Gift Event.
You can find wild Pansage in Pinwheel Forest and Lostlorn Forest.
Trade it with people who have Pokemon White version as you cannot find wild Rufflet in Black
You can't find thundurus in the wild in black. You need to trade one over from white version or GTS.
Actually you will not be able to find a Groudon in pokemon black or white. It's because you will not be able to find a Groudon in the wild. The only way you can get Groudon in pokemon black and white you will have to trade with someone who has a Groudon or you can use Global trade.
Unfortunately, you can't find a wild Pikachu in Pokemon Black. To get it, you need to use PokeTransfer to transfer it from another Pokemon Game, or to find it in the Dream World, and send it to your Entralink. Hope I helped :)