does ancient mew count as mew limiting one to have 4 in a deck , or is its
name ancient mew making 4 of each legal?

It was originally anticipated that due to the fact that Ancient Mew does not have an English equivalent, that it would not even be allowed in DCI sanctioned tournaments at all.  At the STS in Long Beach, though, they ruled that as long as it is played in a sleeve, the card is indeed legal.  For those that do not know what it does, please allow me to give the quick translation:

Ancient Mew
30 HP - Psychic Pokemon
PP : 40
Ret: 2
Weak: P
Resist: None

As far as playing it and mew in the same deck, we have to say yes.  To the best of our knowledge, the official name of the card is "Ancient Mew" which does differ from "Mew".  This means that you may indeed  play 4 of each card.  Excellent question!

Scott