How to revert new deployment to old one in Service Fabric

Revert with "Start-ServiceFabricApplicationUpgrade"

Service Fabric retains old application packages for a while like below. As far as I confirmed, it should retain at least a few hours.

Meanwhile the retainment, you can revert from new deployment to old one with below PowerShell commands.

Login-AzureRmAccount

$applicationName = 'fabric:/FabricApp01'

$connectArgs = @{  ConnectionEndpoint = "'<your cluster name'".westus.cloudapp.azure.com:19000';  
                   X509Credential = $True;  
                   StoreLocation = "CurrentUser";  
                   StoreName = "My";  
                   ServerCommonName = "'your cluster name'.westus.cloudapp.azure.com";  
                   FindType = 'FindByThumbprint';  
                   # "Client certificates" thumbprint. Pick up this value from "security" item in your cluster on Azure Portal
                   FindValue = "YYYYYYYYYY7e3372bc1ed5cf62b435XXXXXXXXXX"; 
                   # "Cluster certificates" thumbprint.  Pick up this value from "security" item in your cluster on Azure Portal
                   ServerCertThumbprint = "YYYYYYYYYY2E67D7E54647A12B7787XXXXXXXXXX" } 
Connect-ServiceFabricCluster @connectArgs

$app = Get-ServiceFabricApplication -ApplicationName $applicationName
$app 
$table = @{}
$app.ApplicationParameters | ForEach-Object { $table.Add( $_.Name, $_.Value)}
Start-ServiceFabricApplicationUpgrade -ApplicationName $applicationName -ApplicationTypeVersion "1.0.2.52" -ApplicationParameter $table -UnmonitoredAuto

You can watch it progress in Service Fabric Explorer like below.

Revert with new Release using existing build packages

I believe you have already made some build packages for deployment into Service Fabric. You can create new Release in your VSTS using the packages like below.