Why conda cannot create environment with python=3.4 installed in it

It seems to me that Python 3.4 is not available in any of your listed repositories. I've tried to create an environment with it in Anaconda and it worked. Try to update Miniconda first:

conda update -n base -c defaults conda

If it does not work, look for a repository containing Python 3.4 and add it to your list of repositories.

The reason you are not able to install python 3.4 package is that it is not available in the default channel of anaconda from where you are trying to install.

However, I just checked that it is available in the conda-forge channel. So, it can be installed as below:

conda create -n myenv python=3.4 -c conda-forge