Azure DNS, how to make what's I created as authoritative

Dear All

The support in MS chat suggested me to post here about this topics.

Okay this is details steps I use in order (I'm not use real domain name/ip address for privacy reasons)

1. I register contoso.xyz with registrar 
2. Then I decide to use Azure DNS as my NS
3. I subscribed to Azure DNS and create contoso.xyz domain resources
4. I created server1.contoso.xyz to point to 1.1.1.80
5. I test with command "nslookup server1.contoso.xyz ns1-04.azure-dns.com" and get the answer as "1.1.1.80"

This is my questions

• What's happen when I use nslookup as above if another user also create contoso.xyz zone and create server1.contoso.xyz to point to 2.2.2.80.
• Does Azure DNS has a method for verify the ownership of each domain zone before it's active that zone ? In the step above I never founded any verification while I can get response from nslookup command.

Regards

Plum