Very serious questions about the bootloader?

Question

linux

I understood how ilnux works, but gaps in understanding still remain. Grab - GRUB2.
1) The grab is located on the fat32 logical partition of the disk, and is mounted in the tree like /boot, right?
2) The grub is configured in /etc/default/grub(1) and /etc/grub.d(2). But, how to set up the hornbeam during the start of the machine, uefi loads the hornbeam kernel into memory and gives it the computer. resources? There is no idea about any root directories yet (initrd and kernel have not yet been loaded).
4) Situation: I started the computer and the bios (uefi) launched the hornbeam. If I just take and configure grub.cfg directly, will the system overwrite all my changes?
3) Grab configures each time a config from files, but at what point in time does it do it? During the reboot, can it turn on?
4) I deleted Grab, or rather erased partition 32, and overwrote a new one, without the possibility of recovery. How do I set up a new hornbeam so that I can log in?
(ubuntu 16/10)

Answer 1

Your curiosity should be satisfied by an article on Habré about loading
There is an article about recovery on Ubuntu Wiki
1) Yes
2) UEFI has no idea about the mount, it launches the appropriate partition.
4) You need to configure other files - here .
3) Well, in general, there is no difference.
4) You need to:
1. Boot from live
2. Mount the desired partition
3. Correct the menu configs (above is a link on how to edit them)
4. Reboot and look at the result of your work.