Hi Gino and Doves,
Gino - you questioned what the mystery is that is spoken of in Revelation 10. If you note what the angel declares, "There will be no more delay", it is obvious to me that this has something to do with time itself. A lot of Bible translations render "delay" as "time". This is declared with tremendous fanfare - drama and noise. It's obviously a biggie and not just a declaration of........."we are going to rush through things now". I truly believe that this stupendous declaration has something to do with Almighty God cutting those days short - as He promised to do. I have linked Revelation 10 below. If one reads through it carefully, I believe it becomes obvious. Our LORD God is not a God of confusion.
Blessings to you, Gino, and all the Doves.https://www.biblegateway.com/passage/?search=Revelation+10&version=NIV