First I built blocks as the left side of picture and I could hear only the 3rd message.
So I changed it as the right side, and I could hear the 1st, 2nd, 3rd messages, but I couldn’t hear twice.
I think that it surely has a connection between this one and the existence of the events as “When ~ After ~” and “When ~ Before ~”.
“Why you can’t wait” says that “Sequential execution in App Inventor means that different blocks can never interrupt each other”.
Then there is no way escaping from the for-next-loop by clicking another button while it is operating.
Is it correct?