What is the name of the grub config file? (Provide only the filename)

Answer: menu.lst

Explanation:
Configuring grub v1
The configuration file is /boot/grub/menu.lst Under Debian, the grub configuration file is updated automatically, when you install a new kernel. This is done automatically by update-grub. You can edit the settings in /boot/grub/menu.lst.Make sure you read the update-grub(8) manpage from your distribution.
Configuring grub v2
The configuration file is /boot/grub/grub.cfg, but you shouldn’t edit it directly. This file is generated by grub v2’s update-grub(8), based on:
1. The script snippets in /etc/grub.d/
2. The configuration file /etc/default/grub
To configure grub “v2”, you should edit /etc/default/grub, then run update-grub. Advanced configuration are achieved by modifying the snippets in /etc/grub.d/.