Answer to Question 1
Io: Molten to core, high density (3600 kg/m3), abundance of sulfur. Surface very active.
Europa: Water ice crust over liquid water ocean over rocky core. Lower density than Io (3000 kg/m3). Surface somewhat active, with only a few fairly new impact craters.
Ganymede, Callisto: Water ice, frozen. Low density (1900 kg/m3). Surface dead and inactive, with many craters.
Answer to Question 2
FALSE