Thank you. I share with you my freshly founded method for adding new POKEDEX ENTRIES into Pokemon RSE/FRLG.
1. Open GBAPGE rom.ini file.
2. Found Pokedex Entries numer and change from 387 to 412.
3. Open POKEDEX ENTRIES EDITOR
4. Every single pointers for new text data first repoint to free space <Founded by FSF>
5. Change your text in Section where you writing Entry and save. Later edit rest information.
FOR TEST.
1. Set by STARTER EDITOR wild New ???? position Pokemon.
2. Use MASTER BALL cheat.
3. Catch them.
4. Look for new great entry of them XD.