How to do a dual boot of two Ubuntu operating systems?

This problem is little bit different than other similar ones.

I have a clone image of Ubuntu production system and plan to propagate it to two different partitions (e.g., /dev/sda1, /dev/sda2).

How to set it up so that the user can choose which one to boot?

Below is what I did so far.

1. boot from rescue cd
2. add a new file /etc/grub.d/11_boot_2 in /dev/sda1
3. point uuid in 11_boot_2 to /dev/sda2
4. chroot to /dev/sda1, and run update-grub
5. modify /etc/fstab in /dev/sda2 to use different mount point

When rebooting, the GRUB menu shows the second boot option. But after choosing it, the boot ends in (initramfs) prompt. The uuid should be correct, because otherwise the boot will print an error like "no such filesystem".

So my questions are:

1. Is any step above wrong, or did I missing anything?

2. At the initramfs stage, what could I do to troubleshoot?

3. Is there any way to enter "grub rescue"? 
   I end up in grub rescue before and I can test boot there. 
   But this time, the system didn't stop at grub rescue.


4. Exactly what stage is initramfs during the whole boot process? 
   That may tell me what is right so far, and what may be wrong.

Thank you so much for the help!

I find this tutorial to be the best source of information regarding GRUB2 - http://www.dedoimedo.com/computers/grub-2.html#mozTocId398970.