1) True.
Uniform circular motion means that the angular velocity

is constant, and since the centripetal acceleration is given by

if

is constant, then a is constant.
2) The correct answer is
a.) the angular velocity and linear velocities are the same
The three knots are in fact on a circle, therefore the angular velocities are the same (because they cover the same angle in the same time) and the linear velocities are the same as well, because it is given by

and since both r(distance from the center) and
are the same, v is also the same.
3) b.) toward the center
In fact, an object can move on a circular path only if there is a force pushing towards the center. This force is called "centripetal force".