I just read through your contest rules and it is as I thought earlier, nowhere do you say that the openmic tag is only for the contest.

You actually state the exact opposite: "You can still post an older video if you want and enter so you can earn on your post, but prize money will not be paid out for those posts. If you want to earn the prize, make a new video and say OPEN MIC Week 40 at the start of it. If you just want to enter and don't care about the prize money, then you still can".

I don't mind playing by the rules but you have to fix that if you expect me to comply.