I have installed Python 3.4.0 and created virtual environment with
python -m venv myenv
Each virtual environment has its own Python binary (allowing creation
of environments with various Python versions) and can have its own
independent set of installed Python packages in its site directories.
It's simply impossible. To create python venv of specific Python version, we need this specific version.
Obviously, Python interpreter doesn't contain all previous versions. Python 3.4.1 doesn't contain Python 2.7.8 executable anywhere inside.