Backup restore from XWiki Enterprise 8.2.1 to 11.9 results 404

I mean I copied the following file

WEB-INF/xwiki.cfg (old XWiki configuration file but still used)
WEB-INF/xwiki.properties (new XWiki Configuration file)
WEB-INF/classes/logback.xml (Logging configuration)
WEB-INF/observation/* (Cluster configuration)

I should not? Or in the xwiki backup/restore docs it’s mentioned just to backup to be on a safer side?

11.9 because I have a test instance where I installed xwiki with this version and got a snapshot of it. So I just have to rollback and try again rather than installing again and again for clean setup.

Is it possible to install 8.2.1 via apt?