1. Earth to Sojourner. We've been terminating the thrust of solids on command since before I was born. It's critical for precisely targeted ballistic missiles. It's also trivially simple.
2. Range safeties require the ability to be built in to any really large solid.
1. Not any more. They use a trajectory optimization maneuvers to use up all the impulse of the motor so that thrust termination systems would not be needed because they were not trivially simple. Or They use liquid in the final stage.
2. It is thrust termination by destruction. They split the whole casing lengthwise.