I have a question in the WebViewer

If I have a WebViewer application and the web page I am using is updated, for example, do they make a change in the application as well, is the change made?

You would need to refresh your web page view for the updates to show, unless you have an updating procedure (javascript) in your webapp that already refreshes the loaded page (client side...)

And how long does it last?

How long does what last?