"Hut' could possibly mean any of those (I don't play rugby myself!), but I think it's more likely to simply mean a wooden building that the teams use as a changing room before and after the match.
Hi, 'Hut two three four' are words used for counting in certain situations. In such a context, 'hut' seems to mean 'one'. I don't know why. It may be a corrupted form of 'up' (as in 'everybody get up on your toes and ready').
Soldiers march to such a count as chanted by their sergeant, and rugby and American football players start some special moves when they hear the c
Yes, although we lack a full context for the original post, I think that your explanation of the term 'hut' here is more likely to be the correct one than is my own.