Hi,
welcome to the VMware communities.
You can use VMware vSphere PowerCLI to answer you questions. PowerCLI is based on Windows PowerShell. So you need that as well.
1. To connect to an ESX server you can use the Connect-VIserver cmdlet:
Connect-VIserver <YourESXServer> -Credential (Get-Credential)
If you can do this, you will know it is an ESX server.
2. To find the list of VMs running on the ESX server you can use the Get-VM cmdlet:
Get-VM
3. To find out which vmware software is running on the server you can use the Get-VMHost cmdlet:
Get-VMHost | Format-List *
This gives you the version and the build of the ESX software, among many other properties.
Regards, Robert