Applied by dribbling 5mls per seam of bees and pro rata for smaller seams. Sorry but it is a judgement call for that part.
It may or may not damage queens, the jury seems to be out on that aspect. It certainly does damage varroa, and I can say that it has been so far my only varroa treatment, and I have yet to find a varroa in my drone brood.
I am hoping the weather cools this week as I am away for a couple of weeks to India and am hoping to get it done before I go, but if not then end of Jan early Feb is not too late.