There are various edits I want to do in HeartGold, but can't find information which will allow me to figure out how:
1. Change the Pokémon encounter information, so that I can add various absent Pokémon into the game.
2. Add the fairy type - including registering it, adding a few basic moves of this type, handling all type-matching info for it, and giving the moves to a few Pokémon. (I also have to give the type to some Pokémon, but I do know how I would do this once I have a type number.)
Unfortunately, I'm using my Android device, and as far as I can tell there are no specialized tools and I'm stuck using a binary editor. I did find both basic Pokémon information (such as a temporary hack to give items to specific species of Pokémon, increasing the XP points I get from them) and the evolution info (replacing trade evolution with level-up, replacing trade-with-item evolution to level-up while holding the item, technically 2 separate from evolutions for day-time and night-time) using Bulbapedia info which was good for Gen 3.