(Continuing from my comment)

These are two completely separate things:

• > type test.ps1
    Write-Host testing
  
  > echo %ERRORLEVEL%
    0
  

  This is just using Get-Content (if you were in the PowerShell console, not cmd.exe) to display the text in the script:
  • thus command being run here is Get-Content, not your script code
  • unless you are doing this at a cmd prompt, then it's DOS type internal command, not Powershell at all

• > powershell -NoProfile -NonInteractive -NoLogo ./test.ps1
    testing
  
  > echo %ERRORLEVEL%
    1
  

  • This is actually running the script, by calling powershell.exe from cmd.exe, and is not an apples-to-apples comparison, leading you to false results.
  • Executing echo %ERRORLEVEL% in a PS shell is meaningless, as PS has no idea what %ERRORLEVEL% is in that use context; to see the last error, you use the PS system error variables, not CMD.exe/DOS stuff.

The code you posted is you doing all things in cmd.exe, not PowerShell; ver is DOS internal command, not a PowerShell command:

• ver /?
  
    Displays the Windows version.
  

  Get-CimInstance -ClassName CIM_OperatingSystem
  
    SystemDirectory     Organization BuildNumber RegisteredUser SerialNumber            Version
    ---------------     ------------ ----------- -------------- ------------            -------
    C:\WINDOWS\system32              19043       Test00         00000-00000-00000-AAOEM 10.0.19043
  

• Just the version:

  (Get-CimInstance -ClassName CIM_OperatingSystem).Version
  
    10.0.19043
  

  
  

See also: Returning an exit code from a PowerShell script