This is how you do it.
Step 1
Start new game.
Step 2
Go to professor Elm's lab. He will ask you to go on an errand and will let you take one of the Pokemon.
Step 3
Now save the game. Take Cyndaquil( because it's first in the line).
Step 4
Go to Mr.Pokemon's house. Get the egg. Get out of there. Professor will call you. So go back to New Bark town.
Step 5
You'll encounter your rival on the way to New Bark Town. Defeat him and continue your journey.
Step 6
When you get to the lab, name your rival. Get out of there. Before you do, one of Elm's aid will give you 5 Pokeballs.
Step 7
Go to the grass and catch any Pokemon.
Step 8
Go to Cherrygrove Pokemon Center. Turn on your PC. Deposit your Cyndaquil. Click on CHANGE BOX. Click on SWITCH. It will ask you to Save your game. Select YES. It will say: SAVING DON'T TURN OFF THE POWER. Turn Off your game before the word POWER ends.
Step 9
Re-open the game. Select Continue. You might be infront of the Pokeballs . Take Totodile. Now go to Cherrygrove Pokemon Center and click on Withdraw Pokemon. If you've done it correctly, Cyndaquil will be there. Don't Withdraw it yet. Do the same thing you did with Cyndaquil. Re-open the game again. Take Chikorita with you. Now go to Cherrygrove Pokemon Center and click on Withdraw Pokemon. Cyndaquil and Totodile might be there. Take them with you.
Step 10
Now you can save that game whenever you want. Because you got all the Starters