MetalGreymon

Q:Can this card's [On Play] effect target the opponent's Digimon that don't have digivolution cards?

A:Yes, it can.

Q:An opponent's Digimon was targeted by this card's [On Play] effect, and after that it gained more digivolution cards than this Digimon has, can it now attack and block again?

A:No. As long as the number of digivolution cards that Digimon had was less than or equal to this Digimon's at the time this effect was activated, this effect stays and it can't attack or block?even if it later gains more digivolution cards.