A disturbingly familiar question...

[Moss Factor]

If a Ditto DS is against a Mew ex, does it have every attack in play or no Power Move alone?

[bulbasnore]

You mean DS38, the 'Mime' Ditto?

Mew ex doesn't have a copy of every attack in play from the Versatile Poké-BODY, it can just USE them.

Versatile - Mew ex can use the attacks of all Pokemon in play as its own. (You still need the necessary Energy to use each attack.) (Poke-BODY)

The attacks that can be used with Versatile are not on Mew ex to copy with DS38's Copy attack.

Copy - Choose 1 of the Defending Pokemon's attacks. Copy copies that attack. This attack does nothing if Ditto doesn't have the Energy necessary to use that attack. (You must still do anything else required for that attack.) Ditto performs that attack.