1) and 2)
Let's sketch the problem and define the coordinate direction:
3)
We know that the height of the ball is 1.5 meters and its initial velocity is zero.
4)
We can write the following equation for the height of the ball h over the time t:
Problem 2.
The acceleration acting on the ball when it goes up is the gravity acceleration.
Its magnitude is equal to 9.8 m/s² and the direction is down (negative y)
The acceleration acting on the ball when it goes down is the same (gravity acceleration: 9.8 m/s² down), since there is no external force acting on the ball.