Dose Omega ring can get Dobly Vision enable??

I hope to see Dolby Vision supported in Blu Ray app as well, but currently only HDR10 is uspported. Dobly vision is supported for streaming.

Nope. Dolby Vision is basically a brand-name for HDR. It's similar to HDR10 format but includes a few different other configurations. And
neither Dobly Vision or HDR are required for 4k.

One thing to be aware of, you must be active in the insider program for a while, and be selected for the alpha ring. You will likely start in the "Omega" ring, and after 1 month you can move up to the "Delta" ring. 3 months will get you
into the "Beta" ring, etc.

In my understanding the Dashboard experiment, A, B, C selection, is totally random.

As "Both consoles say their OS Version is (19h1_release_xbox_dev_1911.191028-1335)" your consoles are either in the Beta or Delta ring.

Both those rings and Omega ring are getting a preview update News release notes Beta Delta Omega
Insiders today, which you can manually start or wait until it becomes mandatory.

After you do the update, if you want to change rings, it will be the perfect time to change as all those rings will be on the same release. Subject to eligibility.

Instead of leaving the Xbox Insider program as one Ambassador has suggested you can drop down to a lower ring which receives much fewer updates. For example if you are in Beta ring drop down to Delta or Omega. The Omega ring receives the fewest updates,
usually just before it is released to the general public. This can be managed using the Xbox Insider Hub on your console.