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Data Export Service: Manual or scheduled exports of your data via the UI. Export Backup Data from Salesforce.
Have a mirror org and possibly have salesforce to salesforce connect for data sync ...
For data use, Data Export Service. For Instance and schema, use VS Code and download all metadata.
Own backup or similar
There are companies that provide this service. I worked for a company who used a third party service which backed up prod and all sandboxes nightly. Don't remember the vendor's name, but a google search should reveal some options for you
We use OwnBackup
Ariel own backup is great and GDPR etc.. compliant
Get a GRAX license and use it for a complete backup