Amity Meadows (Pokewalker Route Info, Japanese)
Rally (Pokewalker Route Info, Japanese)
Sightseeing (Pokewalker Route Info, Japanese)
Yellow Forest (Pokewalker, All Pikachu)
Winner's Path (Pokewalker Route Info)
Source
Yes
Using the infamous DS DNS exploit, you can access old Pokewalker events. Here's directions on how to use this exploit.
Turn on a hotspot on your phone. Wifi routers are no longer made with the same WPS setting that the Nintendo WFC requires. Unless you have a super old router, hotspots are your best bet.
Head to the start menu of your HGSS copy, and go to "Nintendo WFC." Connect to your hotspot.
Once you've connected, find the option to change the settings of your connection, and find the option to change DNS.
Change your DNS to 164.132.44.106.
And that's it! It should be noted that this has a very high chance of not working, but unfortunately there is no way to fix it definitely. Personally, I've never gotten it to work, but you might have better luck than me.
If anyone more experienced with Gen IV DNS notices something wrong with this answer, please let me know. I hope I could help!