Point 1 :

Currenlty, it is not possible to import 2 files with the same name. 

Following error is encountered : 

However, it is possible to rename a file with an already existing name : no error is encountered : 

Point 2 : 

Similar point : 

a - I import a file name "Ametys.jpg". 

b - I rename this file to "Ametys1"

c - I try to import "Ametys.jpg" => Nothing appears (no error message, and file is not imported).