Is it also possible to change the orientation of my donut so that it would face upwards?
To put objects back into World origin, you need to reset their transforms.
You can do it for both Donut and Icing at once.
- Shift Drop the Icing onto the Donut in the outliner. So they move together.
- Select your Donut and clear all transforms one by one. This will put both in center.
- Select Icing and clear Parent relationship (Alt+P). Then go Object > Apply > All Transforms.