Hacked restriction code

You can restore drom a backup that was made before the restriction code was set.

https://support.apple.com/ht204184

It wasn't "hacked". Either you, or someone who knew it changed it, or you forgot.

The only option is to erase the phone using Find My iPhone or by placing it into recovery mode and restoring iOS using iTunes.

Do NOT restore your backup. The backup contains the restriction settings. If you restore your backup, you'll be right back where you started.