virtualenv - Birds Eye View of Understanding
* disclaimer * I mainly use conda environments instead of virtualenv, but I believe that most of this is the same across both of them and is true to your case.

You should be able to access your scripts from any environment you are in. If you have virtenvA and virtenvB then you can access your script from inside either of your environments. All you would do is activate one of them and then run python /path/to/my/script.py, but you need to make sure any dependent libraries are installed. 
Correct, but for clarity the requirements file contains a list of the dependencies by name only. It doesn't contain any actual code or packages. You can print out a requirements file but it should just be a list which  says package names and their version numbers. Like pandas 1.0.1    numpy 1.0.1   scipy 1.0.1 etc.
In the lines of code you have here you would export the dependencies list of env1 and then you would install these dependencies in env2. If env2 was empty then it will now just be a copy of env1, otherwise it will be the same but with all the packages of env1 added and if it had a different version number of some of the same packages then this would be overwritten
Using Windows
Learning about virtualenv. Here is my understanding of it and a few question that I have. Please correct me if my understanding is incorrect. 
virtualenv are environments where your pip dependencies and its selected version are stored for a particular project. A folder is made for your project and inside there are the dependencies. 

I was told you would not want to save your .py scripts in side of virtual ENV, if that's the case how do I access the virtual env when I want to run that project? Open it up in the command line under source ENV/bin/activate then cd my way to where my script is stored?
By running pip freeze that creates a requirements.txt file in that project folder that is just a txt. copy of the dependencies of that virtual env? 
If I'm in a second virutalenv who do I import another virtualenv's requirements? I've been to the documentation but I still don't get it.
$ env1/bin/pip freeze > requirements.txt
$ env2/bin/pip install -r requirements.txt

Guess I'm confused on the "requirements" description. Isn't best practice to always call our requirements, requirements.txt? If that's the case how does env2 know I'm want env1 requirements? 
Thank you for any info or suggestions. Really appreciate the assistance.
I created a virtualenv  C:\Users\admin\Documents\Enviorments>virtualenv django_1 
Using base prefix'c:\\users\\admin\\appdata\\local\\programs\\python\\python37-32' 
New python executable in C:\Users\admin\Documents\Enviorments\django_1\Scripts\python.exe Installing setuptools, pip, wheel...done.
How do I activate it? source django_1/bin/activate doesn't work?
I've tried: source C:\Users\admin\Documents\Enviorments\django_1/bin/activate Every time I get : 'source' is not recognized as an internal or external command, operable program or batch file.