Originally Posted by Fat More Cowbell
I might some time attempt a Diamond Nuzlocke, it sounds cool. I wonder, you can only catch the first Pokémon encountered on every route, right? What if you don't catch it, can you still attempt asecond catch on that route? And can you return to older routes to level your Pokémon a bit?
If you don't catch the first, you won't get a pokemon from that route. Yes, you can level up wherever you want to.