is there a way to get a real ??? monster with the help of a GS ???? Thanx in advance guys :-)

Nope, for most breeds. You can make a few by creating the DNA capsule items with a gameshark, then using them in combinations. But that is a really limited number. (There's a chart in the Items section)

Yes, the GS codes do allow you to make monsters that appear to be rares and enemy monsters by altering the appearance of a monster in the freezer. However, inside, their guts regen rates, lifepatterns, lifespans, statgains, etc. will remain the same as the original monster. So, you won't really have the experience of raising the rare, just the experience of raising an ordinary monster that looks different.

If you have access to a CD burner you can make one with the info in the Laboratory section of the board, that's the best way to make rares.