Pokémon D.W. is a fan made Pokémon game. It is not a ROM hack, but rather a game made in RPG Maker XP, using Pokemon Essentials. This game is just about 100% open world, you can do whatever you like, but the ultimate goal is to escape the town, you can do so by beating the main guard in a Pokébattle. Trade evolutions like seadra into kingdra are handled by using the trade item on them. Levelscaling is enabled for this game, that way you can keep exploring the same maps without overlevelling. The game is a bit dark (not super edgy or anything) so if you don't handle stuff like that very well then I don't recommend you play this game.