I have a PRE site that has all functionality inside (front, sql server, etc) and a PRO farm with four servers (farm- front- sql server- search-owa) and I want to have a working copy on PRE, so in case of error in PRO I can use the PRE site while I repair PRO. I should use Site backup or there is something else I need to do?
First make sure both PRO and PRE are having the same SharePoint versions.
$farm = Get-SPFarm $farm.BuildVersion
Then you can do a Sitecollection backup and restore using PowerShell
Backup-SPSite http://sharepoint.com/sites/site_name -Path C:\Backup\site_name.bak Restore-SPSite http://sharepoint.com/sites/site_name -Path C:\Backup\site_name.bak
If you only want to restore a site(web) then you can save the site as a template and restore it back in PRE.
Recommend way is site collection backup restore.