Question:
I have a question about how the Demon Hearts work, since in theory they give you more hearts when you eat them, and I've tried many ways, but I still don't understand how they work or what you need to do to get more hearts from them

There isn't stated anywhere that you can get bonus hearts from demon hearts, and if it is stated so then it is wrong and should be updated. Eating them will give you a temporary boost only. I will consider adding such functionality, but other mods already implement the permanent bonus hearts feature nicely, so I don't feel like it is necessary in this mod at the moment.

ChatGPT is not a reliable source of info. Most of the time it gives correct information, but when you ask it stuff it may not know that much about, it will just make up stuff on the spot, this is an example of that. As a pro tip in general, you should take responses from AI with a grain of salt and do your own research as well to make sure it is responding somewhat correctly.

Demon Hearts gives the Strength, Nausea and Bloodthirsty effect temporarily, making attacks you do heal you. There is no bonus hearts effect to it, so ChatGPT is really just yapping nonsense. Hope this cleared things up!