what to do if there's no erase all content and settings option?

Follow these instructions to reset the Mac: What to do before you sell, give away, or trade in your Mac - Apple Support

With the release of macOS Monterey, Apple made erasing Mac system easier than ever by adding an Erase All Content and Settings button. If you are using macOS Monterey, then follow the below steps to quickly erase all content and settings on your Mac system:

However, before you consider erasing any content, you should first back up all of your important data. Luckily, Time Machine is one of the best tools for backing up your Mac. Once your data is safe and secure, you can follow the below steps to erase all content and settings on your Mac:

1.    Launch System Preferences.

2.    Click System Preferences in the menu bar and select Erase All Content and Settings.

3.    Enter your admin password when prompted.

4.    Click Continue to confirm that all items will be erased.

5.    Enter your Apple ID and password if prompted to sign out.

6.    Click Erase All Content & Settings to begin the process.

In case you are using lower version than macOS Monterey; then you can restore factory resetting on your Mac using Disk Utility feature.

Hope it helps!