Shellmon

Q:If a Digimon affected by this card's [On Play] [When Digivolving] effect later gains two or more digivolution cards, will it be able to attack and block?

A:No, it will not. This effect targets one of your opponent's Digimon with one or fewer digivolution cards and gives it a "can't attack or block until their turn ends" effect. After the effect is given, it remains on the Digimon even if its digivolution cards increase.