To check for the version update-alternatives 

$ update-alternatives --version

To choosing the Alternative in Manual Mode With config for editors

$ sudo update-alternatives --config editor

To choose the alternative with set

$ sudo update-alternatives --list editor

/bin/ed
/bin/nano
/usr/bin/vim.basic
/usr/bin/vim.tiny

To choose and set manually vim.basic editor

$ sudo update-alternatives --set editor /usr/bin/vim.basic

To set back to auto mode 

$ sudo update-alternatives --auto editor

 Adding New Alternative With install

$ sudo apt install emacs

To make emacs editor available in editor options and set 100 as priority

$ sudo update-alternatives --install /usr/bin/editor editor /usr/bin/emacs 100

$ /usr/bin/editor 

will make open emacs as default editor

To list alternatives with get-selections

$ sudo update-alternatives --get-selections

regards,

T.Dhanasekar