Just one small issue is that, I have to use squashfs image instead of iso image.
The problem in using iso image is that, once initrd job is (almost) over, it runs /bin/run-init which is binary executable,
It tries to remove initramfs filesystem.
As I am mounting ISO inside initramfs, it also tries to delete this iso, and fails. with this failue the init scripts panics and stop the boot process.
11 - 12 July
Could not work much because of Internet connectivity problem.