MANY BALD WORDS

Hello, I have 2 doubts.The first is that I need ManyChat to respond differently depending on the word in a post. That is, in post 1 send an image by typing "b" and send another image by typing the word "b". The detail is that I have 23 words. The other route is to start the conversation with a keyword and in the chat respond with a keyword with an image. Where can I read about it and how can I develop this.