After the event where Master Albert shows his true intentions, you will be presented with four missions. Complete the Highway, The Scrapyard, and The Control Center. After completing those three missions, skip the fourth and go back to Hunter's Camp. Go all the way to the basketball goal and open the way to the Quarry. Complete the mission and you will end up at the entrance of the Quarry. You will not be able to transform back to Model A or any of the transformations until you take the fourth mission you skipped. The transformation will be accessible during the mission. Complete the mission and the area you completed will be opened. However, the events that occurred in the Quarry will be gone and you will not be able to go further in the game.