To find the acceleration function, take the derivative of the velocity function v(t). Acceleration is the rate of change of the velocity with respect to time.
Solve v(t) = 1 to find any values of t in the interval [0, 2] for which this is true.
To find the position function, you can integrate the velocity function, since velocity is the rate of change of position with respect to time.
The particle's initial position occurs at t = 0. Once you obtain the position function, evaluate it at t = 0, and see if there is any other value of t over the interval (0, 4] for which the position function has the same value that it does at t = 0.