Regarding hot or cold milk, it's up to individual preferences. Regarding the order, there is only milk first (unless you like eating a soggy mess of cereal).
Yes, it's supposed to start crunchy and get soggier as you get to the bottom. That is how you get the delicious cereal flavored milk to drink at the end. CEREAL FIRST ALWAYS!!!
Seriously though. Cereal first, cold milk on top. I'll allow the solitary exception of adding cereal to your remaining milk when you only want a little more, or you used the last of the milk.
Honest to god, last week I saw someone take out some instant coffee and a small jar of milk from their backpack in order to get their fix without having to spend the few bucks buying it from a cafe or whatever