Can I initiate a MacOS restart to Recovery mode solely from the command line?
You can do that using the following command:

sudo nvram "recovery-boot-mode=unused"
sudo reboot


This sets a firmware variable in nvram indicating that you want to start in Recovery mode on the next boot, and then reboots the machine.

When done in Recovery mode, run the following from the Terminal in Recovery mode:

nvram -d recovery-boot-mode


This deletes the firmware variable so that the next boot is a normal boot.

If Recovery boot fails and you cannot progress, you could also remove the firmware variable by holding down the keys Command, Option, P, and R during boot. This resets the nvram and thus the firmware variable.