Far as I know, and from my own experience, can't fly indoors in Beginner Mode. Best explanation I could find on Beginner Mode was
HERE. DJI Manual says nothing and couldn't find it in the DJI GO 4 user guide (it's almost impossible to search it). My biggest complaint about DJI is their poor documentation, or the difficulty in finding it when it does exist. (or maybe its just me, getting older is a *****) Did find this yesterday though:
Prevent a Crash or Flyaway with Your DJI Drone (The Complete Guide)
This is an excellent resource.
Sorry for the rant and the Hijack.