Cannot do that, but you can change device name on tether app.

Can you write in English? That will be easier to get answers.

Yes it works with Ethernet backhaul if you connect the second Deco to the main one through Ethernet. By default Deco is in router mode, same for the one you added after the main deco, but actually...

How do you connect those CCs to the router? You may get answers from CCs. Maybe they can tell you what's wrong, what seting is missing.

Saw someone is using the same beta but no such issue. Try reboot your router, login from another web browser. If you don't mind, reset it

Contact tplink support, ask for a solution