I report users who post consecutively when their posts should be merged and the moderator successfully merges them.
It is applied for all forum members, brand representatives of companies that want to make updates or posters who reply in a thread. It's not exclusion for you and your posts in contests too.
Now, since I'm joining contest and need to post my entry maybe 2 or 3 consecutive entries, I'm posting them consecutively rather than into one post.
Depends on the contest rules, you can edit your posts, or delete your past posts and submit a new post with latest versions of your works. To show progress of your art works, you can do it locally with screenshots, videos, and upload it all in a single post, as your contest submission.
If you make reserved post and edit it later, it can be accepted or not accepted by a contest rules.
I suggest two ways that are better than making 2 or 3 consecutive posts as you wanted to do.