Ctrl+6 works for '^'.
I also found "Menu -> Palettes"
There seems to be some other thing to, e.g
  - "Edit->Preferences" doesn't exist.
 
  - auto-completion does not exist
 
  - suggestion bar doesn't exist
 
But I can live with that. Overall Mathematica seems to work fine, and I like it!
I don't know the version number of raspbian, it is the latest.  Linux version 3.18.7-v7+ "cat /proc/version"