I don't think there are rules – you should be able to meditate whenever you want, but it might be interesting to try out and journal how you feel when you meditate before breakfast, after eating sth light, etc.
i don't think there are anu specific written rules, though i believe is better not to eat after meditating. Your is light-weighted in that moment, so i believe you should eat before.
I think meditation in a state where I’m not to full nor too hungry helps me stay in the moment and not get distracted by what my stomach is feeling which sometimes is uncomfortable when hungry or too full.
I think it’s more about how the food makes you feel. You don’t want to be too stuffed or too hungry because it may affect your focus
I like to meditate in the morning before my breakfast, before I start my day, to be more focused on what will come, more focused on my minds.
I have never heard of any rules. What I do is water fasting regularly and I feel so good when I meditate. So I would recommend to meditate on a empty belly. Also note that the digestion is an heavy process for the belly.