Here's a tutorial on how to downgrade tvOS 12 Beta to tvOS 11 / tvOS 11.3 or tvOS 10.2.2 on your Apple TV 4 (1080p model).

Downgrade tvOS 12 Beta to tvOS 11 Today to Resolve Issues and Bring Things to Normal

You're reading this because you want to downgrade tvOS 12 Beta to tvOS 11. It's understandable. tvOS 12 is in beta and it was obvious you'd run into problems and performance related issues. So in order to fix everything up in one fell swoop, downgrading is the way to go. Just follow the steps below and you'll be up and running in no time.

Note: Downgrading will erase everything off your Apple TV.

1. Download the tvOS 11 version you wish to downgrade to. These are the ones Apple is currently signing: tvOS 11.4, tvOS 11.3 and tvOS 10.2.2.

2. Connect your Apple TV with your Mac or PC using a USB-C cable. If you don't have one then it's high time you bought one for yourself.

3. Once your Apple TV is detected, iTunes should launch automatically. If not then launch it manually.

4. Click on the little Apple TV icon in the top left hand corner of iTunes to view more information about your device.

5. Click on Restore Apple TV while holding down the left Option key (Mac) or the left Shift key (Windows).

6. Select the tvOS firmware file you downloaded in step one.

In a few minutes your Apple TV will be restored to tvOS 11.x if all goes well. Once the installation is complete, iTunes will prompt you to disconnect your Apple TV. Disconnect your Apple TV from your PC or Mac and reconnect it to your TV.

That's it. You can now start using your Apple TV normally without having to worry about crashes or any other problems such as app compatibility issues.

If you are truly desperate to use tvOS 12 Beta as your daily driver then I would recommend waiting a couple of betas more. During that time most of the issues will be ironed out and hopefully proceedings should be as smooth as possible.

In the meantime, you may like to check out:

Download tvOS 12 Beta for Apple TV 4 and Apple TV 4K