weight is not constant because it is dependent to the gravitational pull on the referrence...?
No. Velocity includes a direction vector, which speed does not have.
Yes, speed is the scalar of velocity.
no the spring constant is not constant on moon because there is no restoring force there
Constant speed is a fixed rate of displacement of an object. Constant velocity is a fixed rate of displacement in a fixed direction. That might not make sense, but let's dig in a bit and see if we...