Yes, DVFS is enabled by default.  

The status can be checked by cat'ing the sysfs node below:

/sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state

This will provide the time spent in each state, thus verifying that DVFS in enabled.  

The command env erase will restore defaults when executed in the bootloader.

NMCLI should be utilized to configure network interfaces. 

The repo tool is often available to be installed using a package manager. In the case you're facing challenges with this method, or would like to directly add the repo files to your path, the following commands can be used:

sudo wget https://storage.googleapis.com/git-repo-downloads/repo -O /usr/local/bin/repo
sudo chmod a+rx /usr/local/bin/repo

When you run the repo init command for the first time you will be asked to configure your name and email. You can also set these values with the following commands:

git config --global user.email "you@example.com"
git config --global user.name "Your Name"
git config --global color.ui true