Here's the Rule:
"Acceleration" means any change in speed or direction . . .
speeding up, slowing down, or turning.
With just that rule, we can answer everything in this question.
You're on a skateboard, moving very fast but at a constant speed.
We don't know whether you're turning or not. If you're turning,
then you're accelerating. If you're not, then you're not.
Lara Claims that if an object is accelerating, it must be moving.
That's a reasonable claim. If the object is accelerating, then
either its speed or direction is changing. It has to be moving
to do either one.
Lara also claims that if an object is not accelerating, it must be
at rest. This one is NOT a reasonable claim. "Not accelerating"
only means that its speed and direction are not changing. As long
as it's moving at a steady speed in a straight line, it's not accelerating.
In order to chase its tail, a dog has to run in a circle. When he does
that, his direction is constantly changing. That's acceleration.
An airplane moving at a constant speed of 500 miles per hour
in a straight line is not accelerating, because neither its speed
nor its direction is changing.
A race car rounding a corner at a constant speed of 200 miles
per hour is accelerating, because its direction is changing, and
that's one kind of acceleration.
I think we also need to mention that 'acceleration' does NOT mean
'speeding up'. Yes, that's one kind of acceleration, but so are
slowing down and following a curve at constant speed.