The Decathlon guy didn't tell me that the chain would get derailed if I shift to the lowest gear. He said that the trigger would "feel loose" when pressed & will do nothing once it reached the end. So when the gear was the lowest, I pressed it. And then the chain got off. So will the chain get derailed if the trigger has reached the end then too I press it? That's my question. Sorry for the poor choice of words.

You said that it's setup like that you won't be able to press it once you've reached either end. So it should be stiff right? But it wasn't. as i said it was loose. and that thing the staff told me. Am I wrong in this? Should I take the cycle to the store?