Hi All
I have found the solution
I installed RHEL 4 and RHEL 2.1 u5 with two different /boot/efi and / partitions and one common /home partition.
And then at boot-time added the option to boot from one of these partition (a grub, although in 2 color, like choice).
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Linux Guy
Better to understand a little, than to misunderstand a lot.