There’s a solved QR code generator here. It uses IronPython so in Revit 2023 you may need to install the DSIronPython2.7 package for it to work.
To select a specific element i believe you might need to unravel if a web syntax already exists in BIM360 related to element Id’s, and if not a customized forge viewer and code might be able to accept a specific web syntax (e.g. the viewer address followed by an element Id query) to select an element. Beyond my understanding though.