yes

The velocity of a wave which maintains consatnt phase at all successive positions during propogation is known as wave velocity or phase velocity.

The velocity of a group of waves which maintains constant poditions during the propogation is known as group velocity.

The official definition for the word group velocity is "the speed at which the energy of a wave travels."

It isn't. Constant velocity? Uniform velocity across a group of objects?

Group velocity in a waveguide is speed at which EM energy travels in the guide.It will always be less then speed light.