Solved. I did not have to install miui.com rom on both the partitions.
Steps that worked for me:-
1.) Download the zip file from miui.com
2.) Install it using the Updater app or throught Settings>About Phone
3.) After inatallation the phone will reboot
4.) After reboot switch off the phone and start in Recovery mode (press Volume up and power button)
5.) Select Full wipe (I did not try any other option)
6.) Reboot the Phone.
I did notice that after these steps if I tried to restore my backup file made from
the default Backup app my default Browser app would not work.
This might be a problem for other users wanting to use a miui.com rom. I am planing to backup most of data on the Xiaomi account.
Thanks Acid.
P.S. :-
For all members to note, and for the People at Xiaomi, I had ZERO problems
installing a Miuiandroid.com rom onto a Miui.com rom, no app problems, no need for full wipe, nothing.
When I tried to update from one version of Miui.com rom to another Miui.com rom, I had to redo all the above mentioned steps, never had to anything like that with Miuiandroid.com roms.
"Xiaomi, learn from Miuiandroid they could teach you a thing or two."