Is there a way to unlock and restore iPhone 4

The device is locked because of a forgotten passcode? You can sync the iPhone to a computer with the latest version of iTunes. Then put the iPhone in recovery mode.... by holding the power and home button, you will see the apple logo don’t let go until you see an iTunes logo.... Select restore on the computer, the update and restore. Just an FYI this wipes the phone clean like brand new and you will need to know your AppleID and Password.

See here too for instructions: https://support.apple.com/en-us/HT204306

It can be tricky try watching a youtube iphone 4, it helps to see it done!