Hi!
I guess you already enabled 'Version history' on your sharepoint list, right?
If so, this thread discuss how to use action block 'HTTP request to Sharepoint' to get both current item version and last item version.
https://powerusers.microsoft.com/t5/Using-Flows/Using-Values-in-a-Flow-from-JSON-Parse/td-p/461878
It's a long thread, please jump into mesage#8 for the details
Hope this helps