You need to edit AdvanceMap in a hex editor in order for it use expanded Pokemon. Here's how to do it in 1.95 and here's for 1.92. Just remember that you need to include the 25 blank Pokemon between Celebi and Treecko into your calculations. So if your ROM has 649 Pokemon, the number you want to put in will be 674, convert that into hexadecimal (0x2A2) and then reverse the bytes, giving you a result of A2 02 that you put into the hex editor.
A-Starter was made well over a decade ago and doesn't support that sort of stuff. It would be best to edit the Pokeball scripts in Oak's Lab directly if you want to change your starter.
A follow up: I read that 1.95 is a bit buggy and shouldnt be used for anything but wild pokemon placements. Do I need to edit both versions (1.92 and 1.95) and use both accordingly, or is 1.95 enough if I only want to edit wild pokemon and replace/add a few events? (trades, trainers, items)
Remember that Pokedex numbers carries its description as well.
For example Pokedex number of #25 is Pikachu by default.
If you want for example put Pichu as #25. Its Pokedex description will be Pikachu instead of Pichu.
You can swiftly switch these description using Hex Editor, or you can edit each of them manually via PGE which is hell.
In vanilla Firered, I believe these Pokedex description data is stored at 0x44E850, 36 bytes (36 in decimal, 24 in hex) per Pokemon, Here some more details :
0x44E850 = Unknown Pokemon (CF C8 C5 C8 C9 D1 C8 FF 00 00 00 00 00 00 00 00 35 4C 44 08 B1 4C 44 08 00 00 00 01 00 00 00 01 00 00 00 00)
0x44E874 = Bulbasaur (#1)
0x44E898 = Ivysaur (#2)
0x44E8BC = Venusaur (#3)
And so on. (So by this explanation, Charmander should be 44E8BC+24 in HEX which the result will be 0x44E8E0)
If you want to put Pichu as #25. First arrange the Pokedex Number first via PGE which will take some time.
Then to edit its description, go calculate the offset of #25 (Pikachu) and #172 (Pichu)
Copy the #172 (Pichu)36 bytes hexs. Delete it, then paste it to #25 offset.
If done correctly, Pichu will have #25 Pokedex number and the correct description of it.
And Pikachu will be #26 also with correct description.
Hopefully this explanation makes sense. You'll need several easy calculation and ultra focus on this.
I recommend calculate everything on an excel files first. And always take note.
If you have expanded your Pokemon, all those datas will be imported elsewhere, not in 0x44E850 anymore.
So when you expand your Pokemon, take note on where you put those Pokemon Data when you expand your Pokemon.
Or you can check it in your expanded ROM PGE's ini.
@DrFuji I tried using the tutorial, but whether I open the AMap .ini, or the the AMap.exe file in HxD, there is no correct code. In the ini there is nothing even remotely high enough, and in the exe there is only 0077DD0 (instead of 0x77DD5) and even that does not feature the code I am suppossed to alter (9B 01).