Even if it is divided into two SUBDs by removing the surface loop from the object on the left, the selection is done at once, is there an easy way to select the divided objects so that each can be selected?
Oh! I found it myself. You can do it with Explode 
An alternate approach is the Split command using an edge loop as the cutting object. This will create two separate selections.
How do I manipulate it?
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Wondering how to Split command using an edge loop as the cutting object
Run the Split command > Select a SubD > Enter > Click EdgeLoop in the command line > Click an edge or double click an edge to select the loop > Enter.
very very thank you!