Welcome to the Community!
If you mean by “cloud based platform” the Citrix environment, then I would say that the is no such thing available for free just to testing. You need to have your own Citrix environment to test. Citrix by default allows you to install XenApp/XenDesktop on trial 90-day license. You need at least 2-3 servers to make environment (1 x Domain Controller, 1 x Citrix Desktop Delivery Controller and 1 x Citrix XenApp/XenDesktop Worker). So if you have SSD drive and at least 24-32 GB of RAM you can build it on your own computer with VirtualBox or VMware Workstation.
Regarding programs. It depends on you what do you want to automate in Citrix. It can be MS Office, SAP GUI or almost any other application