Question 1
According to Newton's first law, what happens to an object that is already moving when no external unbalanced force is applied?
The right answer is the one marked above.
It keeps moving with uniform velocity. The law has two halves: objects at rest stay at rest, and objects in motion keep moving with uniform velocity.
"It stays at rest" is the first half — that one applies to an object already at rest.
Uniform velocity means both the magnitude and the direction stay unchanged. Producing an acceleration or a retardation needs a force.