Vim Tips

1. remove the last character, if it presents in vim: The following command removes the "," from the end of the line if it presents.

:%s/,$//g

2. ^M in vim
to remove the ^M use %s/<ctrl+V>+ <Enter>//g
press ctrl+v key and then hit Enter key to input ^M in vim command mode.
3. Replace ^with #:
:set number
:10,12s/^/#

Finish replacing you may find that the first column of the file is still in highlight mode, to clear:

use :noh