How do I only allow access to certain folders from a few IPs but not others

Create an IP data group

ltm data-group internal myiplist {
    records {
        1.2.3.4/32 {
            data "/folder1 /folder2 /folder3"
        }
        2.3.4.5/32 {
            data /folder4
        }
        3.4.5.6/32 {
            data "/folder 1 /folder4"
        }
    }
    type ip
}

Then you can have an iRule like:

when HTTP_REQUEST {
  if { [lsearch [class lookup [IP::client_addr] myiplist] [string tolower [HTTP::path]]] == -1 } { discard }
}

might have some syntax wrong there, not currently near a box to test. But basically, you're searching the value of the IP key from the class for the allowed folder, and if it isn't present, discarding the request. You could redirect instead.