Environments, DNS zones and config of Apps on Servers

Dear all,

we are in the process of building a SP2013 dev environment. At the moment we have PROD and UAT.

My question is very much related with SharePoint Add-Ins and the Add-In isolated domain (DNS new zone).

We followed https://technet.microsoft.com/en-us/library/fp161236.aspx to configure the environment for apps for SharePoint. 

Question 1) Does the forward lookup zone created (CompanyApps.com) will also serve the UAT farm or do we have to create a new one for UAT (CompanyAppsUAT.com)?

Question 2) We are following the article https://msdn.microsoft.com/en-us/library/office/fp179923.aspx to set an on-premises dev environment (machine). On the section "Create an isolated add-in domain on your development computer", the msdn article mentions "You must create an isolated domain in your test SharePoint farm"; does this refer to run those powershell commands local on the machine and no need to create the new zone (CompanyDEV.com) in DNS? 

basically do I need as many zones as farm environments?

Thanks in advance for any valuable input here.

Best regards,

Gonçalo

Gonçalo