Solution Steps

1. Use iTunes/Finder: Connect to computer you've synced with → Restore iPhone.
2. Use Recovery Mode: Connect to computer → Hold buttons (varies by model) → Restore in Finder/iTunes.
3. Use iCloud: iCloud.com → Find My iPhone → Erase iPhone (requires Find My enabled).
4. Contact Apple Support if you're locked out of Apple ID.
5. Note: All data will be erased. Restore from backup if available.
6. After restore, you can set up new passcode.