Restoring default settings allows you to reset all phone configurations to the manufacturer's standard.
Note: All data (photos, contacts, messages, etc.) will be permanently erased.
Here's how to restore default settings on OPPO F3 Lite (A57):
Step 1: Access 'Settings' and choose 'Additional Settings'.

Choose 'Additional Settings'.
Step 2: Select 'Backup and Reset'.

Select 'Backup and Reset'.
Step 3: Choose 'Restore Factory Settings'.

Choose 'Restore Factory Settings'.
Step 4: Select 'Erase All Content and Settings'.

Select 'Erase All Content and Settings'.
Step 5: Select 'Delete Data'

Select 'Delete Data'.
Congratulations! The setup process has been completed successfully. Best wishes to all.
