Based on the answers provided, the following corrections need to be made to the 3D object:

1. Modify the shape of the object to be U-shaped. Currently, it is a flat, elongated shape with a rounded end and a straight end. It needs to be transformed into a U-shape to meet the requirement.

2. Add a semi-circle at the bottom of the object. Currently, there is no semi-circle at any end of the object. 

3. Create a circular cutout at the center of the newly added semi-circle. Currently, there is no circular cutout as there is no semi-circle.

4. Ensure that the diameter of the circular cutout is 1/4th the size of the semi-circle's diameter. Currently, this is not applicable as there is no semi-circle or circular cutout.