Android 9, the "hide confidential information" option is enabled. That is, it won't show on the locked screen, but is there a way to only allow certain apps to show?
Yes, there is such a possibility. To do this, go to Settings -> Apps & notifications -> Notification manager. Find the applications you need in the list, go to them. For most applications, there will be a Notifications field on the lock screen, in it you can change what you need. There are different types of notifications for applications like VKontakte and they can be configured for each separately, but the procedure is the same.
After the last update, the message text has stopped showing on the lock screen - only mail icons, watsap, cart, etc. I need the text to be visible immediately, as before. How to do it?