The Featured page only shows the one product sellers enlisted for the feature period. The marketplace sends an e-mail on near the end of each period for the sellers to tell which of their assets will be featured. The Sales event happens in a similar form sent by the marketplace at least one month prior the sales event and where the seller enlist all products and respective discount per asset he want to be part of the sales.
The rotation at page I am not aware the rules, but I thought someone wrote it was a 30min and than updated, that might have changed. The rule would be the same for the Spring Sale and Featured List, but all that might take into account the number of products part of each, so they might self adjust to that number.
A better understanding would require contact directly to the marketplace support or post and Creators Hub.