Reinstalling macOS Monterey on MacBook Pro M1

First, I don’t need to reinstall macOS on MBP M1 but if something happens, how do I reinstall macOS from Disk Utility under recovery mode?

I see two disc sizes. Macintosh HD and Macintosh-Data?

If I want to erase or erase all my data, what data should I erase?
Macintosh HD or Macintosh HD -Data only?

I recently updated to Monterey 12.6.

If I clear both, will that go back to the older version of Monterey which was 12.3?

I’ve searched all over the web and some say to erase both HDs and some say to leave only HD-Data.

Where to locate the official macOS reinstallation tutorial from Apple to reinstall macOS using Disk Utility from Recovery Mode?

Is it true that reinstallation can take 12 hours?