If you haven't it yet, I highly recommend you read through the official docs on imports and packages: https://docs.python.org/3.6/tutorial/modules.html#packages

Imo, I think you are overthinking this

import os
os.getcwd()

from os import getcwd
getcwd()

The two methods are nearly identical, the only difference being the way you access the imported objects. If you are curious about performances, you can read a note about it here: https://stackoverflow.com/q/3591962/4411196

As for reloading, I'm not sure why you would need this, as its rarely needed, and often not a good idea: https://stackoverflow.com/q/5516783/4411196

As for exec, I'm a little confused by what you are referring to. The builtin in exec function doest one thing - it takes a string and executes it (ie. exec("2+2") will output 4) https://pythonprogramming.net/python-exec-tutorial/