Can a publishing client ensure the order of message deliver for, say, five messages, by manipulating the priority of each message from, say, 5 to 1?
No. Message priority is considered by the JMS server and potentially overrides the default first-in-first-out (FIFO) message handling strategy. Priorities should be viewed as one factor that potentially affects the order of message delivery.
The recommended way to ensure the order of message production and reception between the publisher and the consumer is with a transacted session.