Answer:
1) False, since constant speed means constant velocity, but with constant direction as well. Velocity is speed with direction. When you move in a circle, there are boundaries which means that a constant moving speed will cause the object to veer(move in different directions) to maintain movement, If it doesn't veer, the object will deflect(rebound) off the surface due to friction, and impact force or depending on its physical bond of malleability or density.
2a) Create position vectors by drawing a ray from the center(origin) of the circle to each of your desired points, it's magnitude will be the radius(how convenient). Both of these vectors go from the center of the circle to the position on the circle. In general, the distance from the origin to a point is called the radius vector.
2b)