I wonder If Aple TV 4k can playback the new Iphone 12 Pro max Dolby vision 4k HDR videofiles

It can. About 4K, HDR, and Dolby Vision on your Apple TV 4K - Apple Support

Apple TV 4K is built to take full advantage of 4K HDR so you can enjoy TV in the highest quality ever. Apple TV 4K supports the following 4K display formats:

- 4K Standard Dynamic Range (SDR): Used for 4K televisions that don’t support HDR10 or Dolby Vision. 

- 4K High Dynamic Range (HDR): Used for 4K televisions that support HDR to display video with a broader range of colors and luminance.

- 4K Dolby Vision: Used for 4K televisions that support Dolby Vision HDR to display video with a broader range of colors and luminance optimized for your television.

As a follow up to this, even on the latest OS version which is iOS14.2 and tvOS14.2, you cannot AirPlay vidoes recorded in Dolby Vision on Apple TV 4K. They all play in SDR.

I have contacted Apple Support on this and they have no idea.

Like the self recorded 4K video files supported since tvOS 14, it will probably have to be shared through iCloud Photos and the Photos app on Apple TV.

That doesn't surprise me.

I assume you used this but they rarely if ever reply directly:

https://www.apple.com/feedback/appletv.html