I meet these sentences:

      There were six or seven buildings of poured concrete, each three stories high, with screened-in porches punctuating the low clean lines.

      Question:  what's the meaning of screened-in?  the low clean lines?

      The license disappeared (into a crack) smoothly, like a bank card being sucked into an instant-cash machine.

       Question:  what's the meaning of an instant-cash machine?  Please explain this kind of machine.  Is it a ATM?

        Just off the balcony, I could see palm trees with little beaded skirts near the top.

        Question:  what's the meaning of "little beaded skirts near the top"? 

         there were only lush green treetops visible

         Question:  please explain the  grammatical function visible?  Which word does it modify?

          Pat Usher was having a better time than I was too, and I resented that.  I went at it (conversation) again.  Was it Mrs. Peacock in the library with the rope?

           Question:  please explain the meaning of the last sentence:  Was it Mrs. Peacock in the library with the rope?

           Thanks.