The Insider Preview can access beta previews. They can't edit the previews like the Developer Preview and they are also allowed to comment on normal editions, Same with developers for their building teamworks.

Email galaxyos.contact@gmail.com the reason you would like to join.

Developer Previews have much more access for the previews. They can also add things to the OS Beta. If you delete without permission in the slide then you will be removed from the developer preview.

Email galaxyos.contact@gmail.com the reason you would like to join.