In addition to above details, I created this partition as ext4 using fdisk.
The partition is marked as boot partition.
I used grub-install /dev/sda, grub-install /dev/sda1 and grub-install /dev/sda3 to try out the installation following an article about this.
the root partition (/dev/sda3) is ok, has data on it just as before.
I think the kernel image cannot find by the grub. Bcos after installing grub on sda1, no EFI folder, vmlunz and menu.list files are created yet.
When the os boots up, even its welcome screen is not showing up.
I think we need a procedure to restore or install grub to the sda1 by the correct procedure which sme server deserves.