You must play from the start of chapter 3 to 4.
1:-At the start of chapter 3, move over to the mouse holes on the right, zoom in to see a conversation start with trevor. Tap on trevor and he will run to the other hole, proceed to the other hole and tap on Trevor for him to run back to the original hole. Repeat this process until conversation text is repeating the same text or he stops talking.
2:- Then play to the point in chapter 3 where Trevor gives you a key, tap on Trevor repeatedly until conersation text repeats the same text.
3:-Finish chapter 3
4:- Find Trevor at the start of Chapter 4 to the left of the starting room. Make sure to tap on him repeatedly until you see all responses.
5:- Collect the cheese baguette from the control room, feed this to Trevor, this should be the final conversation line that will unlock the achievement.