Thank you very much @SonsOfKorhal,
With all your guidelines and to keep you the happiest as possible, making the best I can, I have finally removed all watermarks during gameplay and added something like a credits section, as a beginning and ending screen, before and after gameplay, with a delay. So, I have included Epic credits and clearly indicated the the demo was created and released by you, and I simply made some little extra changes. Here you are, I hope you like it!:
It’s already published here: Valley of the Ancient - UE5 demo by MARvizer
Thank you very much and best regards!