I've heard that you get the Sinnoh map in HG/SS by getting the Groudon, Kyogue, and Rayquaza is that all true?
No, you cannot obtain the Sinnoh town map in Pokemon HeartGold and SoulSilver considering that you cant even go into the Sinnoh region in those games.
Those Legendaries won't get you anything except help you complete the Pokedex.
You can't get the Sinnoh map, but you can find the Sinnoh Legendary trio Dialga, Palkia, and Giratina! Though, you need the event Arceus for this! Sorry.
How to change your username
How to add a user avatar
Why was my post hidden?
Flags vs Downvotes
Official PokemonDb League
Type a Pokemon name, type, move or ability to see instant results.