How do you make a great achievement in Pokemon LeafGreen mewtwo?

Answer 1

The great achievement is completing the trans-generational trade device on one island. To do this you need to find the ruby and sapphire. The ruby is found on one island at the base of mt.ember, you will see two grunts blocking the path; defeat them and inside you will be in a cave that will lead you to the ruby. The sapphire is found on six island in the dotted hole at the bottom of the island. You will need cut. At the bottom of the island you will reach a ruin after you examine the door use cut on it and it will open. Then inside, at the bottom you will find the sapphire, but the scientist will steal it. He will tell you to go to the rocket warehouse on five island. Go to five island. Defeat the grunts along the way and enter the warehouse. Navigate the warehouse and you will find the scientist. Defeat him he will give you the sapphire. Return to one island and give the ruby and sapphire to Celio. Now you can enter the Cerulean cave.