Using real AdMob ads in alpha/beta testing

Can I use REAL admob ad unit ids when I deploy my app into Google play store Alpha & Beta channels?

Yes, you can, it does not violate the policy.

What if i click or don't click them?

You cannot/should not click on your own live ads.

(well technically you can, but you will get suspended for it)

Technically you can, but there is one very important point to consider - Pre-launch report. You need to either have Pre-launch reports disabled, or make sure you don't show ads to Firebase test devices, or else you will get a bunch of "clicks by bots", with all the consequences.

I just got my account suspended for a month by accidently doing this - don't repeat my mistake.

You can disable Pre-launch reports in Play Console settings (see screenshot), or use this function to somehow hide your ads from testing devices:

boolean isTestDevice() {
    return Boolean.valueOf(Settings.System.getString(getContentResolver(), "firebase.test.lab"));
}

More info in this article on ubuverse.com

Firebase official documentation