This page has directions for how to delete Pokemon save files for every cartridge/console to start a new save, including how to redeem multiple Manaphy Eggs from Pokemon Ranger.
Delete a save file from a GB/GBC cartridge
Start a new game and save. This will overwrite the older save file.
Delete a save file from a GBA cartridge
Start a new game and save. This will overwrite the older save file.
You can also hold Up + Select + B on the title screen.
Alternatively, you can use homebrew on a Custom Firmware Wii to erase the save file.
Delete a save file from a DS cartridge
Hold Up + Select + B on the title screen.
Pokemon Ranger
For Pokemon Ranger, deleting the save file will not make it possible to claim another Manaphy Egg.
However, with a Custom Firmware 3DS it is possible to reset the cartridge entirely.
- With Pokemon Ranger inserted, go to FBI -> titles -> game.
- Go to erase save data and press A.
- If you use Checkpoint to back up the save right before transferring the Manaphy Egg you can easily get the Manaphy Egg repeatedly.
Delete a save file from a 3DS cartridge
Hold Up + B + X on the title screen.
Delete a save file from an Nintendo Switch
- Go to the HOME Menu and select "System Settings".
- Scroll down and select "Data Management".
- Choose "Delete Save Data".
- Select the game title you want to delete the save data for.
- Confirm the deletion when prompted.