is it possible to create two webapplication with the same Port on IIS in PowerShell. I belive it's not extending webapplication. Each Webapplication has her own content data base. Any idea doing that with PowerShell.
As long as you use
Host Headers for both web applications, you should be fine.
Take a look at the New-SPWebapplication cmdlt and be sure to specify the hostheader parameter when creating the web applications.
You need two HostHeaders( DNS), then you can create more than one Web App on single Port.
I.e If you have www.abc.com and www.efg.com, On the Web Application Creation Page. Enter the Name of Web app, Port Number and HostHeader.