The Ansys Learning Hub does take a yearly subscription. The ACT Training for Mechanical there is old. It is a nice place to get started but not absolutely necessary. It focuses on writing ACT extensions, but you learn a lot more about scripting in the training even if you just want to write simple scripts and not ACT extensions.
I tried item.By=Ansys.Mechanical.DataModel.Enums.SetDriverStyle.ResultSet in a native temperature result in 2022 R2, and this worked for me so I don’t know what kind of object you have.
There is a quick definition of the Quantity() here, but you will find it in lots of places in the Scripting in Mechanical Guide:
Speaking of that, some places to learn about scripting can be found in the Ansys help (https://ansyshelp.ansys.com) at:
Mechanical Application > Scripting in Mechanical Guide
Customization Suite > ACT Developer’s Guide
Customization Suite > ACT Customization Guide for Mechanical
At Ansys Customer Portal (https://support.ansys.com/Home/HomePage), go to “Downloads > ACT Resources”
You should explore objects on your own by getting objects from the Outline and using dir(object). You can get the first result item after the “Solution Information” object with:
result1 = ExtAPI.DataModel.Project.Model.Analyses.Children