How does F5 virtual server forwards request based on LTM policies to another virtual server

Thanks for all the detail, it's really helpful to clarify your question.

The virtual command (or virtual selector in LTM policy) simply switches the virtual server of the existing flow. You can do this at a lot of different time-points. If you do this *before* the client-side flow is created, its properties will be inferred from the virtual server that you switch the flow to. If you do it after, the client-side flow will continue.

The node command should infer the destination TCP port from whatever the destination TCP port is of the server-side flow. You can read about that here:

https://clouddocs.f5.com/api/irules/node.html

Here's an in-depth discussion of big-ip architecture that might help understanding:

https://community.f5.com/t5/technical-articles/lightboard-lessons-big-ip-life-of-a-packet/ta-p/287794

If you just want to redirect the user, it's usually a lot easier to just send them an HTTP redirect to the new destination.