I duplicated an existing site for a new project. The existing site already had a favicon uploaded. I want to remove it on the new duplicated site and have no favicon at all. I don’t see a button to remove/delete them. Is this possible?
You can not remove a favicon, if you do not put one, the Webflow logo will be there by default.
Hope this answers your question. 
Not being able to remove and reset the favicon to the default seems like a bug or missing feature to me.
Can you put a transparent .png favicon?
I think so, I prefer you try though, since I have never had no need in doing this, so do not have any experience. 