Issues with Updating Is a backup needed before updating? Will installing new updates have any affect on the pages already saved or the existing structure?
Is a backup needed before updating?


It's definitely recommended.

Regardless of it is an auto-update or a manual update, Craft will attempt to perform a database backup if the backupDbOnUpdate config setting is set to true (it is by default).

If that is set to false you'd want to perform your own backup before doing a Craft update.


  Will installing new updates have any affect on the pages already saved or the existing structure?


Updates should not make breaking changes to the front-end of your site.  The ones that do will be advertised as so, such as the Craft 2 => 3 update process.

You can see the steps that Craft goes through to make sure updating is done safely here: How safe is auto-updating?