Site url and address changes

Hello I would need some advice.

I got a hosting plan for main domain A (akropolis-nuernberg.de) and two addon domains, B (akropolis-hotel-restaurant.de) and C (akropolis-nuernberg.com). All 3 point to the same WP site I have in the root directory and working fine.

In the Settings->General options the following exist:
WordPress address (URL): http://akropolis-hotel-restaurant.de.www383.your-server.de
Website address (URL): http://akropolis-hotel-restaurant.de.www383.your-server.de

This address (WordPress address (URL): http://akropolis-hotel-restaurant.de.www383.your-server.de) is the temporary address I used before I change the DNS. It works fine but we need a clean url like A or B.

Question 1.
If I change these addresses in Settings->General to A will it cause any problem? All sites should load as now and the url will change to A right?

Question 2.
Lets say I want to use the B url which is an addon domain, if I change the Settings->General addresses to B all 3 domains will have this address?

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