Many thanks, Neil! The code worked fine after a minor change. I am trying to make it clear for anybody who might have the same question in the future.
For the output, I had to remove .gdb from "Default.gdb" in order to make it work. So, the output would be "C:/Documents/ArcGIS/Default". I also noticed one interesting thing. All output files were shapefiles (ended with .shp), instead of feature class. Meanwhile, All output files fell outside .gdb. I would definitely like to find out while I get to know more about Python for GIS.
Again, thank Neil, thank Dan!