How to backup settings and list of installed packages?

If I want to make a backup of everything I have done since the fresh install of opensuse,I want to get all the settings that I changed, all the packages I installed, etc.
and how to restore offline?

Not at all sure all that is possible. You can use snapper to roll things back but that does have limits and is not can not be finely divided to restore just part. The only way to do what you want is to make full backups often. If you do incremental backups it will reduce the amount of storage needed.

Note that there are generally two places for config settings in your home and system wide in /etc no history of change are automatically stored

Yast keeps a full history of all installs by day Look in the menu in yast-software management. file is in /var/log/zypp/history

How to make full backups?

Many ways. dd is a great program it will copy and image anything about anywhere. That is good if you want a binary image

To copy just files rsync is great it only copies what has not already been copied to a target. I use luckybackup which is a GUI front end to rsync

But from your descriptions you need an incremental backup. Maybe backintime or dar or kdar

Find what suits you by Yast -Software Management search for backup and check the in description box for a complete list

Then there many commercial backup solutions