If you own the iPhone 4, use iTunes or Finder recovery mode to erase and restore it
Put the iPhone 4 into recovery mode
Connect it to a computer with iTunes installed
Select Restore when prompted
If Find My iPhone is enabled, use iCloud Find My to erase the device
If you know the Apple ID, sign in at iCloud.com and erase the iPhone
If the device is Activation Locked, use the original Apple ID and password after restore
If you forgot the Apple ID password, reset it at iforgot.apple.com
If you have a backup, restore it after the device is unlocked
If you cannot access the Apple ID or computer, contact Apple Support with proof of purchase
Avoid third-party unlocking tools or services that claim to bypass the passcode