RE: prevent a chatbot from asking a question it knows

For this you would need to use <that> in AIML. <that> is used to check a "previous" response.

You could also use a response list using "previous" or "next".

Something like,

<category>
<pattern>I LIKE EATING *</pattern>
<template>What is eating <star/></template>
</category>

<category>
<that>WHAT IS EATING *</that>
<pattern>EATING *</pattern>
<template>Okay, I will remember <self>thatstar.eating = star</self></template>
</category>

<category>
<pattern>WHAT IS EATING *</pattern>
<template><self>if (star.eating == null) { "What is eating " + star; } else { "Eating " + star.eating; }</self></template>
</category>