P.S. I wanted to take this opportunity to inquire whether it's permissible to use one of my Freewrite story series from one of the daily prompts to engage my readers in the story's conclusion by offering a challenge to complete the ending? The story's finale will be as a comment to my post. Thanks in advance for your consideration.

Of course you can! Anything you write is owned by you and you are free to use it as you like! It would be nice if you include a mention of the freewrite daily prompt (a link would be even better!). You can post the challenge in the Freewriters community if you want (and I will put a link to your challenge it in the daily prompt posts)