You don't need to sync anything. If you are going to restore from backup, select "light" when starting the wallet for the first time, then immediately proceed to restoring.
With every Full Backup i have problems look...
When i choose my last backup from 2020 with the newest wallet i have at the import follow error message.

But when i load a older version from thi wallet (2017), after restore, the wallet doesn't synch? The wallet runs about 2 days...
