Slicer uses ITK image reader to load metaimage files. This reader intentionally ignores AnatomicalOrientation (I’ve raised this question before to ITK developers and Kitware and they confirmed that this is not a bug and they will not change the behavior) and considers the image to be in LPS coordinate system. Slicer converts the image to RAS when it is loaded into the scene, and Slicer converts it back to LPS when it is saved to file.
If you want to specify coordinate system using anatomical axes then you need to use nrrd file format.
Yes.