How to set a computer’s primary DNS-Suffix under Windows Server 2012 Core

It's unclear what you mean by "DNS alias name".

The "Primary DNS suffix" is used by the computer to resolve unqualified names. If, for example, you issue the command "ping bob" and your primary DNS suffix is set to "dobbs.com", the DNS resolver will search your HOSTS file for an entry for "bob", then an entry for "bob.dobbs.com", and finally will issue a recursive resolution request to your primary DNS server for the name "bob.dobbs.com".

Basically, the primary DNS suffix is appended to unqualified names by the resolver during recursive resolution requests.

You can use Powershell to show the available Windows Features:

Import-Module ServerManager
Get-WindowsFeature | out-file C:\WindowsFeatures.txt -width 300

Because the data is a long and wide it is better to pipe it into a file and review it there.

it shows that '.NET Framework 3.5 Features' are available, but '.NET Framework 3.5 (includes .NET 2.0 and 3.0)' has been removed.

However, the files are still on the DVD, you can use:

dism /online /enable-feature /featurename:NetFX3 /source:D:\sources\sxs /all /LimitAccess

or the PowerShell 'Add-WindowsFeature' commandlet to install it:

Add-WindowsFeature –name NET-Framework-Core -source D:\sources\sxs

Edit: On Server 2012 R2 with Update 1 installed (KB2919355) this doesn't work if you are using the original DVD/ISO. You need a DVD or ISO which includes that update. For new installations, install .NET 3.5 before you apply KB2919355.