If I understand your question correctly, you want to run the report for all VMs in a vCenter?
In that case, you could change the start of the script to the following.
PS1: I sincerely hope that you are not using such an old PowerCLI version that you need PSSnapin?
PS2: there is a Start-VM at the end of the script. Is that needed?
Connect-VIServer -Server vcenter.local
-User username
-Password Password
Foreach ($vm in Get-VM)
{
$date=Get-Date -format "ddMMyy_HHmm"
Get-AdvancedSetting -Entity $vm | Select Name, Value | Export-CSV $vm"_Before_$date.csv"
New-AdvancedSetting -Entity $vm -Name vmci0.unrestricted -Value FALSE -Confirm:$False -Force:$True
